SCOTLAND has the expertise to potentially equal tech giants like IBM, Google and Intel in the race to develop next-generation computing technologies, scientists believe.

The universities of Edinburgh, Glasgow and Strathclyde have collaborated to form a new national centre that brings together internationally-recognised experts in hardware, software and application development for quantum computing a sector predicted to be worth $65 billion by 2030.

The new Scottish Centre for Innovation in Quantum Computing and Simulation has received funding from the Scottish Government to explore inward investment opportunities.

Quantum computers process information using the properties of tiny microscopic particles or nanoelectronic circuits making them exponentially more powerful than traditional computers. Tech giants including IBM, Google, Microsoft, Intel and Amazon are investing millions of dollars in developing the worlds first workable quantum computers.

Last October, Google announced that its quantum computer took three minutes and 20 seconds to solve a problem that would have taken the worlds fastest supercomputer around 10,000 years to complete.

There are problems that even the worlds biggest supercomputers are unable to solve, said Andrew Daley, a professor of quantum computing at the University of Strathclyde. For example, how to optimise traffic flow by controlling motorways in various places; how to maximise fuel efficiency when big aircraft take off or how to invest in stocks for the maximum reward and minimum risk. Because we can do computing in a very different way on a quantum computer, these are the kinds of things we believe we may be able to do that we can't do on a traditional computer.

Scottish universities are major beneficiaries of the UK governments 1 billion UK National Quantum Technologies Programme, a 10-year drive to put the UK at the forefront of quantum technology research and commercialisation.

Edinburgh University already hosts the UKs 79m national supercomputer and is one of the partners in a 10m project to develop the UKs first commercial quantum computer.

Strathclyde Universitys quantum computing research includes a 10m industry-led project addressing technology barriers to scaling quantum hardware. And Glasgow Universitys projects include being part of a 7m UK consortium aimed at commercialising quantum technologies.

Ivan McKee, Scottish trade, investment and innovation minister, said: This joint project between the universities of Edinburgh, Glasgow and Strathclyde seeks to position Scotland as the go-to location for quantum computing and has the potential to attract significant international research funding and create jobs.

It also provides a model of collaboration which could be applied in other sectors to attract inward investment and boost Scotlands economy.

The Scottish Government funding will finance a feasibility study into inward investment opportunities in quantum computing. These might include partnerships with major technology companies, institutions or countries who already have their own quantum computing programmes.

Microsoft, for example, has quantum computing partnerships with universities and other places in the world, Professor Daley said. There are large centres of quantum computing in Singapore and in the Netherlands at Delft University. The German and US governments have also created clusters in quantum computing and other quantum technologies.

Professor Elham Kashefi, who leads the quantum team at Edinburgh Universitys School of Informatics, believes the new centre could help unlock the potential of quantum tech in an unprecedented way.

She added: Perhaps such a dream could be only achieved at large corporates like IBM, Microsoft, Amazon or Google. Yet I believe the flexibility that the centre could afford as a research institute, compared to a fully business-driven programme, could be the very fundamental bridge that our field desperately needs.

Martin Weides, professor of quantum technologies at Glasgow Universitys James Watt School of Engineering, said: Theres now an international race to realise practical technologies and applications for quantum computing. I believe the Scottish Centre for Innovation in Quantum Computing and Simulation will bring together the strong academic excellence at the three founding universities to give Scotland the edge to develop a vibrant quantum ecosystem.

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University collaboration gives Scotland the edge in global quantum computing race - HeraldScotland

Jiuzhang, a quantum computer prototype developed at the University of Science and Technology of China, represents such a giant leap forward in computing that just 200 seconds of its time dedicated to a specific task would equal 600 million years of computing time for today's current most powerful supercomputer.

On Dec 4, Science magazine announced a major breakthrough made by a team from USTC headed by renowned physicist Pan Jianwei. The team had jointly developed a 76-photon Jiuzhang, realizing an initial milestone on the path to full-scale quantum computing.

This quantum computational advantage, also known as "quantum supremacy", established China's leading position in the sphere of quantum computing research in the world.

USTC has produced a string of wonders: Sending Wukong, China-'s first dark matter particle explorer, and Mozi, the world's first quantum communication satellite, into space; and witnessing the National Synchrotron Radiation Laboratory sending off light from the Hefei Light Source.

During the past 50 years, USTC has made significant achievements in the fields of quantum physics, high-temperature superconductivity, thermonuclear fusion, artificial intelligence and nanomaterials.

Technology is the foundation of a country's prosperity, while innovation is the soul of national progress.

Since 1970, when USTC was relocated to Hefei, Anhui province, it has focused on research and innovation, targeting basic and strategic work in a bid to fulfill its oath to scale "the peak of sciences".

The large number of world-renowned innovative achievements shined glory on USTC, exhibiting its courage to innovate, daring to surpass its peers and unremitting pursuit of striving to be a top university in the world.

Although USTC was set up only 62 years ago, it established the country's first national laboratory and also the first national research center. It has obtained the largest number of achievements selected among China's Top 10 News for Scientific and Technological Progress each year since its founding.

Its reputation as an "important stronghold of innovation" has become stronger over the years.

While facing the frontiers of world science and technology, the main economic battlefield, the major needs of China and people's healthcare, USTC focuses on cultivating high-level scientific and technological innovation talents and teams, and shoulders national tasks.

It has used innovation to generate transformative technologies and develop strategic emerging industries, perfecting its ability to serve national strategic demand, and regional economic and social development.

Facing sci-tech frontiers

USTC has top disciplines covering mathematics, physics, chemistry, Earth and space sciences, biology and materials science. While based on basic research, USTC pays close attention to cutting-edge exploration, encouraging innovative achievements.

Serving major needs

In response to major national needs, USTC has led and participated in a number of significant scientific and technological projects that showcase the nation's strategic aims.

For example, sending the Mozi satellite and Wukong probe into space. Meanwhile, it also participated in the development of core components of Tiangong-2, China's first space lab, and Tianwen-1, the nation's first Mars exploration mission.

Main economic battlefield

In the face of economic and social development needs, USTC has balanced meeting national needs and boosting exploration in frontier spheres.

It has witnessed a series of innovative achievements in the fields of materials science, energy, environment, advanced manufacturing, AI, big data and security.

Safeguarding health

USTC's School of Life Sciences was founded in 1958 with emphasis on biophysics. In recent years, this flourished into many branches of biological sciences.

The new School of Life Sciences was established in Hefei in 1998. Based on its years of cultivation in the field of life sciences, the university has contributed much to China's medical science.

In 2020, the university developed the "USTC protocol" to treat COVID-19 patients, which has been introduced to more than 20 countries and regions.

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Scaling the heights of quantum computing to deliver real results - Chinadaily.com.cn - China Daily

All cryptocurrencies are based on cryptography and require miners to solve extremely complex mathematical problems in order to secure the network. The idea behind quantum computing is that it will be able to crack Bitcoins algorithm much faster than the network.

The basic principle is that Bitcoins network has to be sufficiently fast in order for a quantum attacker to not have enough time to derive the private key of a specific public key before the network.

So far, it seems that quantum computers would take around 8 hours to derive a Bitcoin private key which, in theory, means the network is secure against them. It seems that the mark right now is around 10 minutes. If quantum computers can get close to this time, the Bitcoin network could be compromised.

Its also important to note that quantum computing not only poses a threat to Bitcoin and cryptocurrencies but to other platforms, even banks. Many platforms use encryption which would be broken if quantum computing becomes real, which means the implications of this technology go way beyond just cryptocurrencies.

Theoretically, cryptocurrencies have several ways to mitigate or completely stop quantum computing attacks in the future. For instance, a soft fork on the network of an asset could be enough to at least move some of the assets that are insecure.

Additionally, there are many algorithms that are theorized to be quantum-resistant. In fact, SHA-256 which is currently used should be resistant to these types of attacks. According to recent statistics, around 25% of Bitcoin in circulation remains vulnerable to quantum attacks. You should transfer your coins to a new p2pkh address to make sure they are safe.

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Bitcoin is quantum computing resistant regardless of rising fears among investors - FXStreet

Physicists have confirmed the existence of an extraordinary, flat particle that could be the key that unlocks quantum computing.

Get unlimited access to the weird world of Pop Mech.

What is the rare and improbable anyon, and how on Earth did scientists verify them?

[T]hese particle-like objects only arise in realms confined to two dimensions, and then only under certain circumstanceslike at temperatures near absolute zero and in the presence of a strong magnetic field, Discover explains.

Scientists have theorized about these flat, peculiar particle-like objects since the 1980s, and the very nature of them has made it sometimes seem impossible to ever verify them. But the qualities scientists believe anyons have also made them sound very valuable to quantum research and, now, quantum computers.

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The objects have many possible positions and "remember," in a way, what has happened. In a press release earlier this fall, Purdue University explains more about the value of anyons:

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Its these fractional charges that let scientists finally design the exact right experiments to shake loose the real anyons. A coin sorter is a good analogy for a lot of things, and this time is no different: scientists had to find the right series of sorting ideas in order to build one experimental setup that would, ultimately, only register the anyons. And having the unique quality of fractional charges gave them, at least, a beginning to work on those experiments.

A Quantum Leap in the Classical World

Following an April paper about using a miniature particle accelerator to notice anyons, in July, researchers from Purdue published their findings after using a microchip etched to route particles through a maze that phased out all other particles. The maze combined an interferometera device that uses waves to measure what interferes with themwith a specially designed chip that activates anyons at a state.

Purdue University

What results is a measurable phenomenon called anyonic braiding. This is surprising and good, because it confirms the particle-like anyons exhibit this particular particle behavior, and because braiding as a behavior has potential for quantum computing. Electrons also braid, but researchers werent certain the much weaker charge of anyons would exhibit the same behavior.

Braiding isnt just for electrons and anyons, either: photons do it, too. "Braiding is a topological phenomenon that has been traditionally associated with electronic devices," photon researcher Mikael Rechtsman said in October.

He continued:

Now, the quantum information toolkit includes electrons, protons, and what Discover calls these strange in-betweeners: the anyons.

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This Incredible Particle Only Arises in Two Dimensions - Popular Mechanics

Monday markedtwo years since the passage of the National Quantum Initiative, or NQI Actand in that time, federal agencies followed through on its early calls and helped lay the groundwork for new breakthroughs across the U.S. quantum realm.

Now, the sights of those helping implement the law are set on the future.

I would say in five years, something we'd love to see is ... a better idea of, What are the applications for a quantum computer thats buildable in the next fiveto 10 years, that would be beneficial to society? the Office of Science and Technology Policy Assistant Director for Quantum Information Science Dr. Charles Tahan told Nextgov in an interview Friday. He also serves as the director of the National Quantum Coordination Officea cooperation-pushing hub established by the legislation.

Tahan reflected on some foundational moves made over the last 24 months and offered a glimpse into his teams big-ticket priorities for 2021.

Quantum devices and technologies are among an ever-evolving field that hones in on phenomena at the atomic scale. Potential applications are coming to light, and are expected to radically reshape science, engineering, computing, networking, sensing, communication and more. They offer promises like unhackable internet or navigation support in places disconnected from GPS.

Federal agencies have a long history of exploring physical sciences and quantum-related pursuitsbut previous efforts were often siloed. Signed by President Donald Trump in 2018, the NQI Act sought to provide for a coordinated federal program to accelerate quantum research and development for the economic and national security of America. It assigned specific jobs for the National Institute of Standards and Technology, Energy Department and National Science Foundation, among others, and mandated new collaborations to boost the nations quantum workforce talent pipeline and strengthen societys grasp of this relatively fresh area of investment. The functions of the National Quantum Coordination Office, or NQCO, were also set forth in the bill, and it was officially instituted in early 2019. Since then, the group has helped connect an array of relevant stakeholders and facilitate new initiatives proposed by the law.

Now, everything that's been called out in the act has been establishedits started up, Tahan explained. He noted the three agencies with weighty responsibilities spent 2019 planning out their courses of action within their communities, and this year, subsequently launched weighty new efforts.

One of the latest was unveiled in August by the Energy Department, which awarded $625 million over five yearssubject to appropriationsto its Argonne, Brookhaven, Fermi, Oak Ridge and Lawrence Berkeley national laboratories to establish QIS Research Centers. In each, top thinkers will link up to push forward collaborative research spanning many disciplines. Academic and private-sector institutions also pledged to provide $340 million in contributions for the work.

These are about $25 million eachthat's a tremendous amount of students, and postdocs, and researchers, Tahan said. And those are spread out across the country, focusing on all different areas of quantum: computing, sensing and networking.

NSF this summer also revealed the formation of new Quantum Leap Challenge Institutes to tackle fundamental research hurdles in quantum information science and engineering over the next half-decade. The University of Colorado, University of Illinois-Urbana-Champaign, and University of California, Berkeley are set to head and house the first three institutes, though Tahan confirmed more could be launched next year. The initiative is backed by $75 million in federal fundingand while it will take advantage of existing infrastructures, non-governmental entities involved are also making their own investments and constructing new facilities.

That's the foundation, you know, Tahan said. The teams have been formed, the research plans have been writtenthat's a tremendous amount of workand now they're off actually working. So now, we start to reap the rewards because all the heavy lifting of getting people organized has been done.

Together with NSF, OSTP also helped set in motion the National Q-12 Education Partnership. It intends to connect public, private and academic sector quantum players and cohesively create and release learning materials to help U.S. educators produce new courses to engage students with quantum fields. The work is ultimately meant to spur K-12 students' interest in the emerging areas earlier into their education, and NSF will award nearly $1 million across QIS education efforts through the work.

And beyond the governments walls and those of academia, the NQI Act also presented new opportunities for industry. Meeting the laws requirements, NIST helped convene a consortium of cross-sector stakeholders to strategically confront existing quantum-related technology, standards and workforce gaps, and needs. This year, that groupthe Quantum Economic Development Consortium, or QED-Cbloomed in size, established a more formal membership structure and announced companies that make up its steering committee.

It took a year or more to get all these companies together and then write partnership agreements. So, that partnership agreement was completed towards the beginning of summer, and the steering committee signed it over the summer, and now there are I think 100 companies or so who have signed it, Tahan said. So, it's up and running. It's a real economic development consortiumthats a technical thingand that's a big deal. And how big it is, and how fast it's growing is really, really remarkable.

This fall also brought the launch of quantum.gov, a one-stop website streamlining federal work and policies. The quantum coordination office simultaneously released a comprehensive roadmap pinpointing crucial areas of needed research, deemed the Quantum Frontiers Report.

That assessment incorporates data collected from many workshops, and prior efforts OSTP held to promote the national initiative and establishes eight frontiers that contain core problems with fundamental questions confronting QIS today and must be addressed to push forward research and development breakthroughs in the space. They include expanding opportunities for quantum technologies to benefit society, characterizing and mitigating quantum errors, and more.

It tries to cut through the hype a little bit, Tahan explained. It's a field that requires deep technical expertise. So, it's easy to be led in the wrong direction if you don't have all the data. So we try to narrow it down into here are the important problems, here's what we really don't know, heres what we do know, and go this way, and that will, hopefully benefit the whole enterprise.

Quantum-focused strides have also been made by the U.S. on the international front. Tahan pointed to the first quantum cooperation agreement signed between America and Japan late last year, which laid out basic core values guiding their working together.

We've been using that as a model to engage with other countries. We've had high-level meetings with Australia, industry collaborations with the U.K., and we're engaging with other countries. So, that's progressing, Tahan said. Many countries are interested in quantum as you can guesstheres a lot of investments around the worldand many want to work with us on going faster together.

China had also made its own notable quantum investments (some predating the NQI Act), and touted new claims of quantum supremacy, following Google, on the global stage this year.

I wouldn't frame it as a competition ... We are still very much in the research phase here, and we'll see how those things pan out, Tahan said. I think we're taking the right steps, collectively. The U.S. ecosystem of companies, nonprofits and governments arebased on our strategy, both technical and policiesgoing in the right direction and making the right investments.

Vice President-elect Kamala Harris previously put forthlegislationto broadly advance quantum research, but at this point, the Biden administration hasnt publicly shared any intentions to prioritize government-steered ongoing or future quantum efforts.

[One of] the big things we're looking towards in the next year, is workforce development. We have a critical shortage or need for talent in this space. Its a very diverse set of skills. With these new centers, just do the math. How many students and postdocs are you going to need to fill up those, to do all that research? It's a very large number, Tahan said. And so we're working on something to create that pipeline.

In that light, the team will work to continue to develop NSFs ongoing, Q-12 partnership. Theyll also reflect on whats been built so far through the national initiative to identify any crucial needs that may have been looked over.

As you stand something up thats really big, you're always going to make some mistakes. What have you missed? Tahan noted.

And going forward, the group plans to hone deeper in on balancing the economic and security implications of the burgeoning fields.

As the technology gets more and more advanced, how do we be first to realize everything but also protect our investments? Tahan said. And getting that balance right is going to require careful policy thinking about how to update the way the United States does things.

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Two Years into the Government's National Quantum Initiative - Nextgov

DUBLIN and PARIS, Dec. 17, 2020 Atos today announces it will deliver its first GPU-acceleratedAtos Quantum Learning Machine Enhanced(Atos QLM E), the worlds highest-performing commercially available quantum simulator, to the Irish Centre for High-End Computing (ICHEC).

The Atos QLM E will be integrated with the Irish national supercomputer Kay and equipped with a variety of quantum software programming tools. As a hybrid HPC-Quantum Computing environment, the integrated Kay-Atos QLM E platform will serve theQuantum Programming Ireland (QPI) Initiativefor conducting R&D and national-level skills development activities in quantum technologies by ICHEC as well as other Irish organizations in academic, enterprise and public sector.

Offering up to 12 times more computation speed than the original Atos QLM, the Atos QLM E is also an integral component of the NEASQC project, in the 1 bn European flagship quantum initiative, of which Ireland is a partner along with 11 other European companies and research labs, andcoordinated by Atos.

Once the Atos QLM E is delivered on-premise, Atos will provide a fast-track training program and continue to enhance the system throughout its lifetime to ensure that it delivers the functionality required in this fast-moving discipline of quantum computing.

Prof. Jean-Christophe (JC) Desplat, Director at ICHEC, said:As Irelands high performance computing authority, were committed to using the power of technology to solve some of the toughest challenges across public, academic and enterprise sectors. Working with a number of partners across Europe, we look forward to utilizing the Atos QLM E related for R&D on a number of scientific and industry-relevant quantum computing use-casesand supporting scientific breakthroughs in high-performance computing.

Agns Boudot, Senior Vice President, Head of HPC & Quantum at Atos, said:As the first Atos QLM E deployed globally, this partnership marks an important milestone in our Quantum Program. We look forward to supporting ICHEC on their quantum journey, helping them explore with their users the huge potential that quantum computing offers. The solution will provide a scalable, future-proof, national framework for the porting of hybrid applications, and for the training and skills development of Irish researchers, and ICHECs partners across Europe.

Atos QLM E has been optimized to drastically reduce the simulation time of hybrid classical-quantum algorithms simulations, leading to quicker progress in application research.

Atos, a pioneer in quantum

In 2016, Atos launched Atos Quantum an ambitiousprogram to anticipate the future of quantum computing. As a result of this initiative,Atos was the first organization to offer aquantum noise simulation modulewithin its Atos QLM offer. Atos QLM is being used in numerous countries worldwide includingAustria,Finland,France,Germany,India, Italy,Japan,the Netherlands, Senegal,UKand theUnited States, empowering major research programs in various sectors like industry orenergy. Recently, Atos introduced Q-score, the first universal quantum metrics reference, applicable to all programmable quantum processors.

Source: Atos

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Atos Delivers Its First GPU-Accelerated Quantum Learning Machine to the Irish Centre for High-End Computing - HPCwire

By GREGORY ZELLER //

The Stony Brook University scientist who came in from the cold is getting some serious chills and this time, hes really got something to cryo about.

Slowa Solovyov, a multi-patented, 23-year veteran of U.S. Department of Energy collaborations, is diving into the coldest environments man can create on a quest to improve quantum-level efficiencies. The longtime SBU adjunct professor of electrical engineering is flipping the switch on Next Cryo, a startup enterprise focused on reducing quantum-computing losses through the composition of new materials and the application of some truly frigid temperatures.

Trained at the Moscow Institute for Physics and Technology (masters degree in applied physics) and Ukraines G.V. Kurdyumov Institute for Metal Physics (PhD in solid-state physics), Solovyov is no rookie entrepreneur: In 2015, along with Brookhaven Technology Group President Paul Farrell, he launched NextSwitch, an ambitious startup focused on high-temperature superconductivity.

High-temperature superconductivity is slightly misleading high references temperatures above 77 degrees Kelvin (roughly minus 321 degrees Fahrenheit), which is frosty on your skin but the boiling point of liquid nitrogen, a primary cryogenics coolant.

Cold-blooded: Slowa Solovyov, with cryogenics coursing through his veins.

When you operate in the quantum world, you want to reduce noise and temperature is what makes noise, Solovyov noted. Temperature destroys connections between quanta, or information.

With his new startup, Mr. Freeze will really chill out. The typical MRI machine operates around absolute zero (about minus 460 degrees Fahrenheit), but quantum computers turn things down significantly from there, operating at temperatures about 50 times lower, according to Solovyov.

The innovator envisions the commercialization of cutting-edge materials that not only allow quantum computers to do their thing with reduced quanta degradation, but could benefit multiple sciences where cold is hot, including superconducting magnets, fusion reactors and other cutting-edge tech.

Upon launch, scheduled for January 2021, Next Cryos basic plan is simple: materials preparation and testing at SBUs Advanced Energy Research and Technology Center, validation at Brookhaven National Laboratory (Solovyov is an old friend) and a series of customer pilots with major quantum-computing companies, according to the scientist, with on-point customer feedback eventually informing a breakthrough product.

The startup a client of SBUs Clean Energy Business Incubator Program, along with the Brookhaven Technology Group should have a good idea of what the product will look like by this time next year, Solovyov added.

There are a lot of different solutions and approaches, he said. But what the product should actually look like is the goal of this customer-discovery process.

Next Cryo

Whats It? Next-gen R&D focused on improving super-cold supercomputing

Brought To You By: From-Russia-with-doctorates Stony Brook University adjunct Slowa Solovyov, whos bundled up before

Status: Cooling off for a hot start in 2021

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With Next Cryo, a startup that's really cooling its jets - Innovate Long Island - Innovate Long Island

Dec. 18, 2020 Super-fast quantum computers and communication devices could revolutionize countless aspects of our livesbut first, researchers need a fast, efficient source of the entangled pairs of photons such systems use to transmit and manipulate information. Researchers at Stevens Institute of Technology have done just that, not only creating a chip-based photon source 100 times more efficient that previously possible, but bringing massive quantum device integration within reach.

Its long been suspected that this was possible in theory, but were the first to show it in practice, said Yuping Huang, Gallagher associate professor of physics and director of the Center for Quantum Science and Engineering.

To createphoton pairs, researchers trap light in carefully sculpted nanoscale microcavities; as light circulates in the cavity, its photons resonate and split into entangled pairs. But theres a catch: at present, such systems are extremely inefficient, requiring a torrent of incoming laser light comprising hundreds of millions of photons before a single entangled photon pair will grudgingly drip out at the other end.

Huang and colleagues at Stevens have now developed a new chip-based photon source thats 100 times more efficient than any previous device, allowing the creation of tens of millions of entangled photon pairs per second from a single microwatt-powered laser beam.

This is a huge milestone for quantum communications, said Huang, whose work will appear in the Dec. 17 issue ofPhysical Review Letters.

Working with Stevens graduate students Zhaohui Ma and Jiayang Chen, Huang built on his laboratorys previous research to carve extremely high-quality microcavities into flakes of lithium niobate crystal. The racetrack-shaped cavities internally reflect photons with very little loss of energy, enabling light to circulate longer and interact with greater efficiency.

By fine-tuning additional factors such as temperature, the team was able to create an unprecedentedly bright source of entangled photon pairs. In practice, that allows photon pairs to be produced in far greater quantities for a given amount of incoming light, dramatically reducing the energy needed to power quantum components.

The team is already working on ways to further refine their process, and say they expect to soon attain the true Holy Grail of quantum optics: a system with that can turn a single incoming photon into an entangled pair of outgoing photons, with virtually no waste energy along the way. Its definitely achievable, said Chen. At this point we just need incremental improvements.

Until then, the team plans to continue refining their technology, and seeking ways to use theirphotonsource to drive logic gates and other quantum computing or communication components. Because this technology is already chip-based, were ready to start scaling up by integrating other passive or active optical components, explained Huang.

The ultimate goal, Huang said, is to make quantum devices so efficient and cheap to operate that they can be integrated into mainstream electronic devices. We want to bring quantum technology out of the lab, so that it can benefit every single one of us, he explained. Someday soon we want kids to have quantum laptops in their backpacks, and were pushing hard to make that a reality.

More information:Ultrabright quantum photon sources on chip,Physical Review Letters(2020).arxiv.org/abs/2010.04242,journals.aps.org/prl/accepted/ da6c4d64a454565839ae

Source: Stevens Institute of Technology

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Chip-Based Photon Source Is 100X More Efficient than Previous, Bringing Quantum Integration Within Reach - HPCwire

Study of a model of computation

Quantum computing is the use of quantum phenomena such as superposition and entanglement to perform computation. Computers that perform quantum computations are known as quantum computers.[1]:I-5 Quantum computers are believed to be able to solve certain computational problems, such as integer factorization (which underlies RSA encryption), substantially faster than classical computers. The study of quantum computing is a subfield of quantum information science.

Quantum computing began in the early 1980s, when physicist Paul Benioff proposed a quantum mechanical model of the Turing machine.[2]Richard FeynmanandYuri Maninlater suggested that a quantum computer had the potential to simulate things that a classical computer could not.[3][4] In 1994, Peter Shor developed a quantum algorithm for factoring integers that had the potential to decrypt RSA-encrypted communications.[5] Despite ongoing experimental progress since the late 1990s, most researchers believe that "fault-tolerant quantum computing [is] still a rather distant dream."[6] In recent years, investment into quantum computing research has increased in both the public and private sector.[7][8] On 23 October 2019, Google AI, in partnership with the U.S. National Aeronautics and Space Administration (NASA), claimed to have performed a quantum computation that is infeasible on any classical computer.[9]

There are several models of quantum computers (or rather, quantum computing systems), including the quantum circuit model, quantum Turing machine, adiabatic quantum computer, one-way quantum computer, and various quantum cellular automata. The most widely used model is the quantum circuit. Quantum circuits are based on the quantum bit, or "qubit", which is somewhat analogous to the bit in classical computation. Qubits can be in a 1 or 0 quantum state, or they can be in a superposition of the 1 and 0 states. However, when qubits are measured the result of the measurement is always either a 0 or a 1; the probabilities of these two outcomes depend on the quantum state that the qubits were in immediately prior to the measurement.

Progress towards building a physical quantum computer focuses on technologies such as transmons, ion traps and topological quantum computers, which aim to create high-quality qubits.[1]:213 These qubits may be designed differently, depending on the full quantum computer's computing model, whether quantum logic gates, quantum annealing, or adiabatic quantum computation. There are currently a number of significant obstacles in the way of constructing useful quantum computers. In particular, it is difficult to maintain the quantum states of qubits as they suffer from quantum decoherence and state fidelity. Quantum computers therefore require error correction.[10][11]

Any computational problem that can be solved by a classical computer can also be solved by a quantum computer.[12] Conversely, any problem that can be solved by a quantum computer can also be solved by a classical computer, at least in principle given enough time. In other words, quantum computers obey the ChurchTuring thesis. While this means that quantum computers provide no additional advantages over classical computers in terms of computability, quantum algorithms for certain problems have significantly lower time complexities than corresponding known classical algorithms. Notably, quantum computers are believed to be able to quickly solve certain problems that no classical computer could solve in any feasible amount of timea feat known as "quantum supremacy." The study of the computational complexity of problems with respect to quantum computers is known as quantum complexity theory.

The prevailing model of quantum computation describes the computation in terms of a network of quantum logic gates.[13] This model can be thought of as an abstract linear-algebraic generalization of a classical circuit. Since this circuit model obeys quantum mechanics, a quantum computer capable of efficiently running these circuits is believed to be physically realizable.

A memory consisting of n {textstyle n} bits of information has 2 n {textstyle 2^{n}} possible states. A vector representing all memory states thus has 2 n {textstyle 2^{n}} entries (one for each state). This vector is viewed as a probability vector and represents the fact that the memory is to be found in a particular state.

In the classical view, one entry would have a value of 1 (i.e. a 100% probability of being in this state) and all other entries would be zero. In quantum mechanics, probability vectors are generalized to density operators. This is the technically rigorous mathematical foundation for quantum logic gates, but the intermediate quantum state vector formalism is usually introduced first because it is conceptually simpler. This article focuses on the quantum state vector formalism for simplicity.

We begin by considering a simple memory consisting of only one bit. This memory may be found in one of two states: the zero state or the one state. We may represent the state of this memory using Dirac notation so that

| 0 := ( 1 0 ) ; | 1 := ( 0 1 ) {displaystyle |0rangle :={begin{pmatrix}1\0end{pmatrix}};quad |1rangle :={begin{pmatrix}0\1end{pmatrix}}}

| := | 0 + | 1 = ( ) ; | | 2 + | | 2 = 1. {displaystyle |psi rangle :=alpha ,|0rangle +beta ,|1rangle ={begin{pmatrix}alpha \beta end{pmatrix}};quad |alpha |^{2}+|beta |^{2}=1.}

The state of this one-qubit quantum memory can be manipulated by applying quantum logic gates, analogous to how classical memory can be manipulated with classical logic gates. One important gate for both classical and quantum computation is the NOT gate, which can be represented by a matrix

X := ( 0 1 1 0 ) . {displaystyle X:={begin{pmatrix}0&1\1&0end{pmatrix}}.}

The mathematics of single qubit gates can be extended to operate on multiqubit quantum memories in two important ways. One way is simply to select a qubit and apply that gate to the target qubit whilst leaving the remainder of the memory unaffected. Another way is to apply the gate to its target only if another part of the memory is in a desired state. These two choices can be illustrated using another example. The possible states of a two-qubit quantum memory are

| 00 := ( 1 0 0 0 ) ; | 01 := ( 0 1 0 0 ) ; | 10 := ( 0 0 1 0 ) ; | 11 := ( 0 0 0 1 ) . {displaystyle |00rangle :={begin{pmatrix}1\0\0\0end{pmatrix}};quad |01rangle :={begin{pmatrix}0\1\0\0end{pmatrix}};quad |10rangle :={begin{pmatrix}0\0\1\0end{pmatrix}};quad |11rangle :={begin{pmatrix}0\0\0\1end{pmatrix}}.}

C N O T := ( 1 0 0 0 0 1 0 0 0 0 0 1 0 0 1 0 ) . {displaystyle CNOT:={begin{pmatrix}1&0&0&0\0&1&0&0\0&0&0&1\0&0&1&0end{pmatrix}}.}

In summary, a quantum computation can be described as a network of quantum logic gates and measurements. However, any measurement can be deferred to the end of a quantum computation, though this deferment may come at a computational cost, so most quantum circuits depict a network consisting only of quantum logic gates and no measurements.

Any quantum computation (which is, in the above formalism, any unitary matrix over n {displaystyle n} qubits) can be represented as a network of quantum logic gates from a fairly small family of gates. A choice of gate family that enables this construction is known as a universal gate set, since a computer that can run such circuits is a universal quantum computer. One common such set includes all single-qubit gates as well as the CNOT gate from above. This means any quantum computation can be performed by executing a sequence of single-qubit gates together with CNOT gates. Though this gate set is infinite, it can be replaced with a finite gate set by appealing to the Solovay-Kitaev theorem. The representation of multiple qubits can be shown as Qsphere.

Progress in finding quantum algorithms typically focuses on this quantum circuit model, though exceptions like the quantum adiabatic algorithm exist. Quantum algorithms can be roughly categorized by the type of speedup achieved over corresponding classical algorithms.[14]

Quantum algorithms that offer more than a polynomial speedup over the best known classical algorithm include Shor's algorithm for factoring and the related quantum algorithms for computing discrete logarithms, solving Pell's equation, and more generally solving the hidden subgroup problem for abelian finite groups.[14] These algorithms depend on the primitive of the quantum Fourier transform. No mathematical proof has been found that shows that an equally fast classical algorithm cannot be discovered, although this is considered unlikely.[15] Certain oracle problems like Simon's problem and the BernsteinVazirani problem do give provable speedups, though this is in the quantum query model, which is a restricted model where lower bounds are much easier to prove, and doesn't necessarily translate to speedups for practical problems.

Other problems, including the simulation of quantum physical processes from chemistry and solid state physics, the approximation of certain Jones polynomials, and the quantum algorithm for linear systems of equations have quantum algorithms appearing to give super-polynomial speedups and are BQP-complete. Because these problems are BQP-complete, an equally fast classical algorithm for them would imply that no quantum algorithm gives a super-polynomial speedup, which is believed to be unlikely.[16]

Some quantum algorithms, like Grover's algorithm and amplitude amplification, give polynomial speedups over corresponding classical algorithms.[14] Though these algorithms give comparably modest quadratic speedup, they are widely applicable and thus give speedups for a wide range of problems.[17] Many examples of provable quantum speedups for query problems are related to Grover's algorithm, including Brassard, Hyer, and Tapp's algorithm for finding collisions in two-to-one functions,[18] which uses Grover's algorithm, and Farhi, Goldstone, and Gutmann's algorithm for evaluating NAND trees,[19] which is a variant of the search problem.

A notable application of quantum computation is for attacks on cryptographic systems that are currently in use. Integer factorization, which underpins the security of public key cryptographic systems, is believed to be computationally infeasible with an ordinary computer for large integers if they are the product of few prime numbers (e.g., products of two 300-digit primes).[20] By comparison, a quantum computer could efficiently solve this problem using Shor's algorithm to find its factors. This ability would allow a quantum computer to break many of the cryptographic systems in use today, in the sense that there would be a polynomial time (in the number of digits of the integer) algorithm for solving the problem. In particular, most of the popular public key ciphers are based on the difficulty of factoring integers or the discrete logarithm problem, both of which can be solved by Shor's algorithm. In particular, the RSA, DiffieHellman, and elliptic curve DiffieHellman algorithms could be broken. These are used to protect secure Web pages, encrypted email, and many other types of data. Breaking these would have significant ramifications for electronic privacy and security.

Identifying cryptographic systems that may be secure against quantum algorithms is an actively researched topic under the field of post-quantum cryptography. [21][22] Some public-key algorithms are based on problems other than the integer factorization and discrete logarithm problems to which Shor's algorithm applies, like the McEliece cryptosystem based on a problem in coding theory.[21][23]Lattice-based cryptosystems are also not known to be broken by quantum computers, and finding a polynomial time algorithm for solving the dihedral hidden subgroup problem, which would break many lattice based cryptosystems, is a well-studied open problem.[24] It has been proven that applying Grover's algorithm to break a symmetric (secret key) algorithm by brute force requires time equal to roughly 2n/2 invocations of the underlying cryptographic algorithm, compared with roughly 2n in the classical case,[25] meaning that symmetric key lengths are effectively halved: AES-256 would have the same security against an attack using Grover's algorithm that AES-128 has against classical brute-force search (see Key size).

Quantum cryptography could potentially fulfill some of the functions of public key cryptography. Quantum-based cryptographic systems could, therefore, be more secure than traditional systems against quantum hacking.[26]

The most well-known example of a problem admitting a polynomial quantum speedup is unstructured search, finding a marked item out of a list of n {displaystyle n} items in a database. This can be solved by Grover's algorithm using O ( n ) {displaystyle O({sqrt {n}})} queries to the database, quadratically fewer than than the ( n ) {displaystyle Omega (n)} queries required for classical algorithms. In this case, the advantage is not only provable but also optimal: it has been shown that Grover's algorithm gives the maximal possible probability of finding the desired element for any number of oracle lookups.

Problems that can be addressed with Grover's algorithm have the following properties:[citation needed]

For problems with all these properties, the running time of Grover's algorithm on a quantum computer will scale as the square root of the number of inputs (or elements in the database), as opposed to the linear scaling of classical algorithms. A general class of problems to which Grover's algorithm can be applied[27] is Boolean satisfiability problem. In this instance, the database through which the algorithm is iterating is that of all possible answers. An example (and possible) application of this is a password cracker that attempts to guess the password or secret key for an encrypted file or system. Symmetric ciphers such as Triple DES and AES are particularly vulnerable to this kind of attack.[citation needed] This application of quantum computing is a major interest of government agencies.[28]

Since chemistry and nanotechnology rely on understanding quantum systems, and such systems are impossible to simulate in an efficient manner classically, many believe quantum simulation will be one of the most important applications of quantum computing.[29] Quantum simulation could also be used to simulate the behavior of atoms and particles at unusual conditions such as the reactions inside a collider.[30] Quantum simulations might be used to predict future paths of particles and protons under superposition in the double-slit experiment.[citation needed] About 2% of the annual global energy output is used for Nitrogen fixation to produce ammonia for the Haber process in the agricultural fertilizer industry while naturally occurring organisms also produce ammonia. Quantum simulations might be used to understand this process increasing production.[31]

Quantum annealing or Adiabatic quantum computation relies on the adiabatic theorem to undertake calculations. A system is placed in the ground state for a simple Hamiltonian, which is slowly evolved to a more complicated Hamiltonian whose ground state represents the solution to the problem in question. The adiabatic theorem states that if the evolution is slow enough the system will stay in its ground state at all times through the process.

Since quantum computers can produce outputs that classical computers cannot produce efficiently, and since quantum computation is fundamentally linear algebraic, some express hope in developing quantum algorithms that can speed up machine learning tasks.[32][33] For example, the quantum algorithm for linear systems of equations, or "HHL Algorithm", named after its discoverers Harrow, Hassidim, and Lloyd, is believed to provide speedup over classical counterparts.[34][33]

John Preskill has introduced the term quantum supremacy to refer to the hypothetical speedup advantage that a quantum computer would have over a classical computer in a certain field.[35]Google announced in 2017 that it expected to achieve quantum supremacy by the end of the year though that did not happen. IBM said in 2018 that the best classical computers will be beaten on some practical task within about five years and views the quantum supremacy test only as a potential future benchmark.[36] Although skeptics like Gil Kalai doubt that quantum supremacy will ever be achieved,[37][38] in October 2019, a Sycamore processor created in conjunction with Google AI Quantum was reported to have achieved quantum supremacy,[39] with calculations more than 3,000,000 times as fast as those of Summit, generally considered the world's fastest computer.[40]Bill Unruh doubted the practicality of quantum computers in a paper published back in 1994.[41]Paul Davies argued that a 400-qubit computer would even come into conflict with the cosmological information bound implied by the holographic principle.[42]

There are a number of technical challenges in building a large-scale quantum computer.[43] Physicist David DiVincenzo has listed the following requirements for a practical quantum computer:[44]

Sourcing parts for quantum computers is also very difficult. Many quantum computers, like those constructed by Google and IBM, need Helium-3, a nuclear research byproduct, and special superconducting cables that are only made by the Japanese company Coax Co.[45]

The control of multi qubit systems requires the generation and coordination of a large number of electrical signals with tight and deterministic timing resolution. This had led to the development of quantum controllers which enable interfacing the qubit. Scaling these systems to support a growing number of qubits is an additional challenge in the scaling of quantum computers.[citation needed]

One of the greatest challenges involved with constructing quantum computers is controlling or removing quantum decoherence. This usually means isolating the system from its environment as interactions with the external world cause the system to decohere. However, other sources of decoherence also exist. Examples include the quantum gates, and the lattice vibrations and background thermonuclear spin of the physical system used to implement the qubits. Decoherence is irreversible, as it is effectively non-unitary, and is usually something that should be highly controlled, if not avoided. Decoherence times for candidate systems in particular, the transverse relaxation time T2 (for NMR and MRI technology, also called the dephasing time), typically range between nanoseconds and seconds at low temperature.[46] Currently, some quantum computers require their qubits to be cooled to 20 millikelvins in order to prevent significant decoherence.[47] A 2020 study argues that ionizing radiation such as cosmic rays can nevertheless cause certain systems to decohere within milliseconds.[48]

As a result, time-consuming tasks may render some quantum algorithms inoperable, as maintaining the state of qubits for a long enough duration will eventually corrupt the superpositions.[49]

These issues are more difficult for optical approaches as the timescales are orders of magnitude shorter and an often-cited approach to overcoming them is optical pulse shaping. Error rates are typically proportional to the ratio of operating time to decoherence time, hence any operation must be completed much more quickly than the decoherence time.

As described in the Quantum threshold theorem, if the error rate is small enough, it is thought to be possible to use quantum error correction to suppress errors and decoherence. This allows the total calculation time to be longer than the decoherence time if the error correction scheme can correct errors faster than decoherence introduces them. An often cited figure for the required error rate in each gate for fault-tolerant computation is 103, assuming the noise is depolarizing.

Meeting this scalability condition is possible for a wide range of systems. However, the use of error correction brings with it the cost of a greatly increased number of required qubits. The number required to factor integers using Shor's algorithm is still polynomial, and thought to be between L and L2, where L is the number of qubits in the number to be factored; error correction algorithms would inflate this figure by an additional factor of L. For a 1000-bit number, this implies a need for about 104 bits without error correction.[50] With error correction, the figure would rise to about 107 bits. Computation time is about L2 or about 107 steps and at 1MHz, about 10 seconds.

A very different approach to the stability-decoherence problem is to create a topological quantum computer with anyons, quasi-particles used as threads and relying on braid theory to form stable logic gates.[51][52]

Physicist Mikhail Dyakonov has expressed skepticism of quantum computing as follows:

There are a number of quantum computing models, distinguished by the basic elements in which the computation is decomposed. The four main models of practical importance are:

The quantum Turing machine is theoretically important but the physical implementation of this model is not feasible. All four models of computation have been shown to be equivalent; each can simulate the other with no more than polynomial overhead.

For physically implementing a quantum computer, many different candidates are being pursued, among them (distinguished by the physical system used to realize the qubits):

A large number of candidates demonstrates that quantum computing, despite rapid progress, is still in its infancy.[citation needed]

Any computational problem solvable by a classical computer is also solvable by a quantum computer.[80] Intuitively, this is because it is believed that all physical phenomena, including the operation of classical computers, can be described using quantum mechanics, which underlies the operation of quantum computers.

Conversely, any problem solvable by a quantum computer is also solvable by a classical computer; or more formally, any quantum computer can be simulated by a Turing machine. In other words, quantum computers provide no additional power over classical computers in terms of computability. This means that quantum computers cannot solve undecidable problems like the halting problem and the existence of quantum computers does not disprove the ChurchTuring thesis.[81]

As of yet, quantum computers do not satisfy the strong Church thesis. While hypothetical machines have been realized, a universal quantum computer has yet to be physically constructed. The strong version of Church's thesis requires a physical computer, and therefore there is no quantum computer that yet satisfies the strong Church thesis.

While quantum computers cannot solve any problems that classical computers cannot already solve, it is suspected that they can solve many problems faster than classical computers. For instance, it is known that quantum computers can efficiently factor integers, while this is not believed to be the case for classical computers. However, the capacity of quantum computers to accelerate classical algorithms has rigid upper bounds, and the overwhelming majority of classical calculations cannot be accelerated by the use of quantum computers.[82]

The class of problems that can be efficiently solved by a quantum computer with bounded error is called BQP, for "bounded error, quantum, polynomial time". More formally, BQP is the class of problems that can be solved by a polynomial-time quantum Turing machine with error probability of at most 1/3. As a class of probabilistic problems, BQP is the quantum counterpart to BPP ("bounded error, probabilistic, polynomial time"), the class of problems that can be solved by polynomial-time probabilistic Turing machines with bounded error.[83] It is known that BPP {displaystyle subseteq } BQP and is widely suspected that BQP {displaystyle nsubseteq } BPP, which intuitively would mean that quantum computers are more powerful than classical computers in terms of time complexity.[84]

The exact relationship of BQP to P, NP, and PSPACE is not known. However, it is known that P {displaystyle subseteq } BQP {displaystyle subseteq } PSPACE; that is, all problems that can be efficiently solved by a deterministic classical computer can also be efficiently solved by a quantum computer, and all problems that can be efficiently solved by a quantum computer can also be solved by a deterministic classical computer with polynomial space resources. It is further suspected that BQP is a strict superset of P, meaning there are problems that are efficiently solvable by quantum computers that are not efficiently solvable by deterministic classical computers. For instance, integer factorization and the discrete logarithm problem are known to be in BQP and are suspected to be outside of P. On the relationship of BQP to NP, little is known beyond the fact that some NP problems that are believed not to be in P are also in BQP (integer factorization and the discrete logarithm problem are both in NP, for example). It is suspected that NP {displaystyle nsubseteq } BQP; that is, it is believed that there are efficiently checkable problems that are not efficiently solvable by a quantum computer. As a direct consequence of this belief, it is also suspected that BQP is disjoint from the class of NP-complete problems (if an NP-complete problem were in BQP, then it would follow from NP-hardness that all problems in NP are in BQP).[86]

The relationship of BQP to the basic classical complexity classes can be summarized as follows:

It is also known that BQP is contained in the complexity class #P (or more precisely in the associated class of decision problems P#P),[86] which is a subclass of PSPACE.

It has been speculated that further advances in physics could lead to even faster computers. For instance, it has been shown that a non-local hidden variable quantum computer based on Bohmian Mechanics could implement a search of an N {displaystyle N} -item database in at most O ( N 3 ) {displaystyle O({sqrt[{3}]{N}})} steps, a slight speedup over Grover's algorithm, which runs in O ( N ) {displaystyle O({sqrt {N}})} steps. Note, however, that neither search method would allow quantum computers to solve NP-complete problems in polynomial time.[87] Theories of quantum gravity, such as M-theory and loop quantum gravity, may allow even faster computers to be built. However, defining computation in these theories is an open problem due to the problem of time; that is, within these physical theories there is currently no obvious way to describe what it means for an observer to submit input to a computer at one point in time and then receive output at a later point in time.[88][89]

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Quantum computing - Wikipedia

Quantum computing is an area of study focused on the development of computer based technologies centered around the principles ofquantum theory. Quantum theory explains the nature and behavior of energy and matter on thequantum(atomic and subatomic) level. Quantum computing uses a combination ofbitsto perform specific computational tasks. All at a much higher efficiency than their classical counterparts. Development ofquantum computersmark a leap forward in computing capability, with massive performance gains for specific use cases. For example quantum computing excels at like simulations.

The quantum computer gains much of its processing power through the ability for bits to be in multiple states at one time. They can perform tasks using a combination of 1s, 0s and both a 1 and 0 simultaneously. Current research centers in quantum computing include MIT, IBM, Oxford University, and the Los Alamos National Laboratory. In addition, developers have begun gaining access toquantum computers through cloud services.

Quantum computing began with finding its essential elements. In 1981, Paul Benioff at Argonne National Labs came up with the idea of a computer that operated with quantum mechanical principles. It is generally accepted that David Deutsch of Oxford University provided the critical idea behind quantum computing research. In 1984, he began to wonder about the possibility of designing a computer that was based exclusively on quantum rules, publishing a breakthrough paper a few months later.

Quantum Theory

Quantum theory's development began in 1900 with a presentation by Max Planck. The presentation was to the German Physical Society, in which Planck introduced the idea that energy and matter exists in individual units. Further developments by a number of scientists over the following thirty years led to the modern understanding of quantum theory.

Quantum Theory

Quantum theory's development began in 1900 with a presentation by Max Planck. The presentation was to the German Physical Society, in which Planck introduced the idea that energy and matter exists in individual units. Further developments by a number of scientists over the following thirty years led to the modern understanding of quantum theory.

The Essential Elements of Quantum Theory:

Further Developments of Quantum Theory

Niels Bohr proposed the Copenhagen interpretation of quantum theory. This theory asserts that a particle is whatever it is measured to be, but that it cannot be assumed to have specific properties, or even to exist, until it is measured. This relates to a principle called superposition. Superposition claims when we do not know what the state of a given object is, it is actually in all possible states simultaneously -- as long as we don't look to check.

To illustrate this theory, we can use the famous analogy of Schrodinger's Cat. First, we have a living cat and place it in a lead box. At this stage, there is no question that the cat is alive. Then throw in a vial of cyanide and seal the box. We do not know if the cat is alive or if it has broken the cyanide capsule and died. Since we do not know, the cat is both alive and dead, according to quantum law -- in a superposition of states. It is only when we break open the box and see what condition the cat is in that the superposition is lost, and the cat must be either alive or dead.

The principle that, in some way, one particle can exist in numerous states opens up profound implications for computing.

A Comparison of Classical and Quantum Computing

Classical computing relies on principles expressed by Boolean algebra; usually Operating with a 3 or 7-modelogic gateprinciple. Data must be processed in an exclusive binary state at any point in time; either 0 (off / false) or 1 (on / true). These values are binary digits, or bits. The millions of transistors and capacitors at the heart of computers can only be in one state at any point. In addition, there is still a limit as to how quickly these devices can be made to switch states. As we progress to smaller and faster circuits, we begin to reach the physical limits of materials and the threshold for classical laws of physics to apply.

The quantum computer operates with a two-mode logic gate:XORand a mode called QO1 (the ability to change 0 into a superposition of 0 and 1). In a quantum computer, a number of elemental particles such as electrons or photons can be used. Each particle is given a charge, or polarization, acting as a representation of 0 and/or 1. Each particle is called a quantum bit, or qubit. The nature and behavior of these particles form the basis of quantum computing and quantum supremacy. The two most relevant aspects of quantum physics are the principles of superposition andentanglement.

Superposition

Think of a qubit as an electron in a magnetic field. The electron's spin may be either in alignment with the field, which is known as aspin-upstate, or opposite to the field, which is known as aspin-downstate. Changing the electron's spin from one state to another is achieved by using a pulse of energy, such as from alaser. If only half a unit of laser energy is used, and the particle is isolated the particle from all external influences, the particle then enters a superposition of states. Behaving as if it were in both states simultaneously.

Each qubit utilized could take a superposition of both 0 and 1. Meaning, the number of computations a quantum computer could take is 2^n, where n is the number of qubits used. A quantum computer comprised of 500 qubits would have a potential to do 2^500 calculations in a single step. For reference, 2^500 is infinitely more atoms than there are in the known universe. These particles all interact with each other via quantum entanglement.

In comparison to classical, quantum computing counts as trueparallel processing. Classical computers today still only truly do one thing at a time. In classical computing, there are just two or more processors to constitute parallel processing. EntanglementParticles (like qubits) that have interacted at some point retain a type can be entangled with each other in pairs, in a process known ascorrelation. Knowing the spin state of one entangled particle - up or down -- gives away the spin of the other in the opposite direction. In addition, due to the superposition, the measured particle has no single spin direction before being measured. The spin state of the particle being measured is determined at the time of measurement and communicated to the correlated particle, which simultaneously assumes the opposite spin direction. The reason behind why is not yet explained.

Quantum entanglement allows qubits that are separated by large distances to interact with each other instantaneously (not limited to the speed of light). No matter how great the distance between the correlated particles, they will remain entangled as long as they are isolated.

Taken together, quantum superposition and entanglement create an enormously enhanced computing power. Where a 2-bit register in an ordinary computer can store only one of four binary configurations (00, 01, 10, or 11) at any given time, a 2-qubit register in a quantum computer can store all four numbers simultaneously. This is because each qubit represents two values. If more qubits are added, the increased capacity is expanded exponentially.

Quantum Programming

Quantum computing offers an ability to write programs in a completely new way. For example, a quantum computer could incorporate a programming sequence that would be along the lines of "take all the superpositions of all the prior computations." This would permit extremely fast ways of solving certain mathematical problems, such as factorization of large numbers.

The first quantum computing program appeared in 1994 by Peter Shor, who developed a quantum algorithm that could efficiently factorize large numbers.

The Problems - And Some Solutions

The benefits of quantum computing are promising, but there are huge obstacles to overcome still. Some problems with quantum computing are:

There are many problems to overcome, such as how to handle security and quantum cryptography. Long time quantum information storage has been a problem in the past too. However, breakthroughs in the last 15 years and in the recent past have made some form of quantum computing practical. There is still much debate as to whether this is less than a decade away or a hundred years into the future. However, the potential that this technology offers is attracting tremendous interest from both the government and the private sector. Military applications include the ability to break encryptions keys via brute force searches, while civilian applications range from DNA modeling to complex material science analysis.

This was last updated in June 2020

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