Google announced this fall to much fanfare that it had demonstrated quantum supremacy that is, it performed a specific quantum computation far faster than the best classical computers could achieve. IBM promptly critiqued the claim, saying that its own classical supercomputer could perform the computation at nearly the same speed with far greater fidelity and, therefore, the Google announcement should be taken with a large dose of skepticism.

This wasnt the first time someone cast doubt on quantum computing. Last year, Michel Dyakonov, a theoretical physicist at the University of Montpellier in France, offered a slew of technical reasons why practical quantum supercomputers will never be built in an article in IEEE Spectrum, the flagship journal of electrical and computer engineering.

So how can you make sense of what is going on?

As someone who has worked on quantum computing for many years, I believe that due to the inevitability of random errors in the hardware, useful quantum computers are unlikely to ever be built.

Whats a quantum computer?

To understand why, you need to understand how quantum computers work since theyre fundamentally different from classical computers.

A classical computer uses 0s and 1s to store data. These numbers could be voltages on different points in a circuit. But a quantum computer works on quantum bits, also known as qubits. You can picture them as waves that are associated with amplitude and phase.

Qubits have special properties: They can exist in superposition, where they are both 0 and 1 at the same time, and they may be entangled so they share physical properties even though they may be separated by large distances. Its a behavior that does not exist in the world of classical physics. The superposition vanishes when the experimenter interacts with the quantum state.

Due to superposition, a quantum computer with 100 qubits can represent 2100 solutions simultaneously. For certain problems, this exponential parallelism can be harnessed to create a tremendous speed advantage. Some code-breaking problems could be solved exponentially faster on a quantum machine, for example.

There is another, narrower approach to quantum computing called quantum annealing, where qubits are used to speed up optimization problems. D-Wave Systems, based in Canada, has built optimization systems that use qubits for this purpose, but critics also claim that these systems are no better than classical computers.

Regardless, companies and countries are investing massive amounts of money in quantum computing. China has developed a new quantum research facility worth US$10 billion, while the European Union has developed a 1 billion ($1.1 billion) quantum master plan. The United States National Quantum Initiative Act provides $1.2 billion to promote quantum information science over a five-year period.

Breaking encryption algorithms is a powerful motivating factor for many countries if they could do it successfully, it would give them an enormous intelligence advantage. But these investments are also promoting fundamental research in physics.

Many companies are pushing to build quantum computers, including Intel and Microsoft in addition to Google and IBM. These companies are trying to build hardware that replicates the circuit model of classical computers. However, current experimental systems have less than 100 qubits. To achieve useful computational performance, you probably need machines with hundreds of thousands of qubits.

Noise and error correction

The mathematics that underpin quantum algorithms is well established, but there are daunting engineering challenges that remain.

For computers to function properly, they must correct all small random errors. In a quantum computer, such errors arise from the non-ideal circuit elements and the interaction of the qubits with the environment around them. For these reasons the qubits can lose coherency in a fraction of a second and, therefore, the computation must be completed in even less time. If random errors which are inevitable in any physical system are not corrected, the computers results will be worthless.

In classical computers, small noise is corrected by taking advantage of a concept known as thresholding. It works like the rounding of numbers. Thus, in the transmission of integers where it is known that the error is less than 0.5, if what is received is 3.45, the received value can be corrected to 3.

Further errors can be corrected by introducing redundancy. Thus if 0 and 1 are transmitted as 000 and 111, then at most one bit-error during transmission can be corrected easily: A received 001 would be a interpreted as 0, and a received 101 would be interpreted as 1.

Quantum error correction codes are a generalization of the classical ones, but there are crucial differences. For one, the unknown qubits cannot be copied to incorporate redundancy as an error correction technique. Furthermore, errors present within the incoming data before the error-correction coding is introduced cannot be corrected.

Quantum cryptography

While the problem of noise is a serious challenge in the implementation of quantum computers, it isnt so in quantum cryptography, where people are dealing with single qubits, for single qubits can remain isolated from the environment for significant amount of time. Using quantum cryptography, two users can exchange the very large numbers known as keys, which secure data, without anyone able to break the key exchange system. Such key exchange could help secure communications between satellites and naval ships. But the actual encryption algorithm used after the key is exchanged remains classical, and therefore the encryption is theoretically no stronger than classical methods.

Quantum cryptography is being commercially used in a limited sense for high-value banking transactions. But because the two parties must be authenticated using classical protocols, and since a chain is only as strong as its weakest link, its not that different from existing systems. Banks are still using a classical-based authentication process, which itself could be used to exchange keys without loss of overall security.

Quantum cryptography technology must shift its focus to quantum transmission of information if its going to become significantly more secure than existing cryptography techniques.

Commercial-scale quantum computing challenges

While quantum cryptography holds some promise if the problems of quantum transmission can be solved, I doubt the same holds true for generalized quantum computing. Error-correction, which is fundamental to a multi-purpose computer, is such a significant challenge in quantum computers that I dont believe theyll ever be built at a commercial scale.

[ Youre smart and curious about the world. So are The Conversations authors and editors. You can get our highlights each weekend. ]

Subhash Kak, Regents Professor of Electrical and Computer Engineering, Oklahoma State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Image: Reuters

Go here to see the original:

Quantum Computers Are the Ultimate Paper Tiger - The National Interest Online

- Total to crunch the numbers on 'nanoporus' materials to hone carbon capture - Recharge - May 24th, 2020
- Total partners with Cambridge Quantum Computing on CO2 capture - Green Car Congress - May 20th, 2020
- Seeqc UK Awarded 1.8M In Grants To Advance Quantum Computing Initiatives - Business Wire - May 20th, 2020
- Atos and CSC empower the Finnish quantum research community with Atos Quantum Learning Machine - Quantaneo, the Quantum Computing Source - May 20th, 2020
- Light Waves Used to Access Unique Properties of the Quantum World - AZoQuantum - May 20th, 2020
- Weekly Update: Global Coronavirus Impact and Implications on Quantum Computing Market Forecast Report Offers Key Insights, Key Drivers, Technology -... - May 20th, 2020
- Quantum computing will (eventually) help us discover vaccines in days - VentureBeat - May 16th, 2020
- Registration Open for Inaugural IEEE International Conference on Quantum Computing and Engineering (QCE20) - PRNewswire - May 16th, 2020
- Quantum Computing Market Research Report 2020 By Size, Share, Trends, Analysis and Forecast to 2026 - Cole of Duty - May 16th, 2020
- The Global Quantum Dots Market is expected to grow from USD 2,581.12 Million in 2018 to USD 10,423.13 Million by the end of 2025 at a Compound Annual... - May 16th, 2020
- Quantum computing analytics: Put this on your IT roadmap - TechRepublic - May 15th, 2020
- David Graves to Head New Research at PPPL for Plasma Applications in Industry and Quantum Information Science - Quantaneo, the Quantum Computing... - May 15th, 2020
- Registration Open for Inaugural IEEE International Conference on Quantum Computing and Engineering - HPCwire - May 15th, 2020
- Seeqc UK Awarded 1.8M in Grants to Advance Quantum Computing Initiatives - HPCwire - May 15th, 2020
- Yale College 2020: Meet some of the graduates - Yale News - May 15th, 2020
- Quantum Computing Market Growth Trends, Key Players, Analysis, Competitive Strategies and Forecasts to 2026 - News Distinct - May 15th, 2020
- Video: The Future of Quantum Computing with IBM - insideHPC - May 14th, 2020
- Topological Quantum Computing Market Growth by Top Companies, Trends by Types and Application, Forecast to 2026 - Cole of Duty - May 14th, 2020
- IonQ CEO Peter Chapman on how quantum computing will change the future of AI - VentureBeat - May 14th, 2020
- New Tool Could Pave the Way for Future Insights in Quantum Chemistry - AZoQuantum - May 14th, 2020
- Daily AI Roundup: The Coolest Things on Earth Today - AiThority - May 14th, 2020
- Research Fellow in Geometric Topology job with UNIVERSITY OF LEEDS | 206608 - Times Higher Education (THE) - May 14th, 2020
- Archer to work alongside IBM in progressing quantum computing - ZDNet - May 6th, 2020
- A Discovery That Long Eluded Physicists: Superconductivity to the Edge - SciTechDaily - May 6th, 2020
- Physicists Criticize Stephen Wolfram's 'Theory of Everything' - Scientific American - May 6th, 2020
- Virtual ICM Seminar: 'HPC Simulations of the Early Universe' - HPCwire - May 6th, 2020
- 9 great reads from CNET this week - CNET - May 4th, 2020
- Devs: Here's the real science behind the quantum computing TV show - New Scientist News - May 4th, 2020
- IBM Announces a Quantum Challenge With Four Exercises to Solve in 4 Days - Database Trends and Applications - May 4th, 2020
- New Princeton study takes superconductivity to the edge - Princeton University - May 4th, 2020
- Quantum Computing Market Inclinations And Development Status Highlighted During Forecast Period 2019-2026 - Latest Herald - April 29th, 2020
- Meet the new bipartisan consensus on China, just as wrong as the old bipartisan consensus on China - Greenwich Time - April 29th, 2020
- Trump betting millions to lay the groundwork for quantum internet in the US - CNBC - April 28th, 2020
- Wiring the Quantum Computer of the Future: Researchers from Japan and Australia propose a novel 2D design - QS WOW News - April 28th, 2020
- Announcing the IBM Quantum Challenge - Quantaneo, the Quantum Computing Source - April 28th, 2020
- Muquans and Pasqal partner to advance quantum computing - Quantaneo, the Quantum Computing Source - April 28th, 2020
- Deltec Bank, Bahamas - Quantum Computing Will bring Efficiency and Effectiveness and Cost Saving in Baking Sector - marketscreener.com - April 28th, 2020
- The world doesn't want to pick between the U.S. and China - The Advocate - April 28th, 2020
- COVID-19 will accelerate AI's replacement of humans as factor of production | TheHill - The Hill - April 13th, 2020
- IoT news of the week for April 10, 2020 - Stacey on IoT - April 13th, 2020
- Global Quantum Computing Market To Grow at a Stayed CAGR with Huge Profits by 2025 | D-Wave Systems Inc. (Canada) - Fashion Trends News - April 13th, 2020
- 'Westworld': Rehoboam name inspired by sci-fi book 'Stand on Zanzibar' - Insider - INSIDER - April 13th, 2020
- Quantum Computing: What You Need To Know - Inc42 Media - April 9th, 2020
- Microsoft invests in PsiQuantum, a startup which is building the worlds first useful quantum computer - MSPoweruser - MSPoweruser - April 9th, 2020
- HQS and AQT Announce Strategic Partnership - HPCwire - April 9th, 2020
- Prysmian Group Selects IBM To Help Accelerate Digital Transformation With Adoption of IBM Cloud - PRNewswire - April 9th, 2020
- Quantum computing at the nanoscale - News - The University of Sydney - April 8th, 2020
- Securing IoT in the Quantum Age - Eetasia.com - April 8th, 2020
- Inside the Global Race to Fight COVID-19 Using the World's Fastest Supercomputers - Scientific American - April 8th, 2020
- Global Quantum Computing Market 2025 company profile of each organization are entailed in the study : D-Wave Systems, Google, IBM, Intel, Microsoft,... - April 8th, 2020
- D-Wave makes its quantum computers free to anyone working on the coronavirus crisis - VentureBeat - April 1st, 2020
- Can Quantum Computing Be the New Buzzword - Analytics Insight - April 1st, 2020
- Q-CTRL to Host Live Demos of 'Quantum Control' Tools - Quantaneo, the Quantum Computing Source - April 1st, 2020
- We're Getting Closer to the Quantum Internet, But What Is It? - HowStuffWorks - April 1st, 2020
- Who Will Mine Cryptocurrency in the Future - Quantum Computers or the Human Body? - Coin Idol - April 1st, 2020
- Universities Space Research Association to Lead a DARPA Project on Quantum Computing - Quantaneo, the Quantum Computing Source - April 1st, 2020
- The Schizophrenic World Of Quantum Interpretations - Forbes - April 1st, 2020
- Disrupt The Datacenter With Orchestration - The Next Platform - April 1st, 2020
- Quantum Computing strikes technology partnership with Splunk - Proactive Investors USA & Canada - March 26th, 2020
- Devs: Alex Garland on Tech Company Cults, Quantum Computing, and Determinism - Den of Geek UK - March 26th, 2020
- Is Machine Learning The Quantum Physics Of Computer Science ? - Forbes - March 26th, 2020
- Recent PDF Report : Quantum Computing Market 2020: In-depth Industry Analysis By Size, Share, Competition, Opportunities And Growth By 2029 - Sound On... - March 26th, 2020
- Organisms grow in wave pattern, similar to ocean circulation - Big Think - March 26th, 2020
- Tech incubator Fountech.Ventures launches in US and UK - UKTN - March 26th, 2020
- Why resilience is the key to future security - Raconteur - March 22nd, 2020
- Quantum computing is right around the corner, but cooling is a problem. What are the options? - Diginomica - March 21st, 2020
- Quantum Computing: Will It Actually Produce Jobs? - Dice Insights - March 21st, 2020
- Quantum computing, AI, China, and synthetics highlighted in 2020 Tech Trends report - VentureBeat - March 16th, 2020
- Early investment in quantum computing could result in a competitive advantage - Help Net Security - March 16th, 2020
- Quantum Computing for Everyone - The Startup - Medium - March 16th, 2020
- UC Riverside to lead scalable quantum computing project using 3D printed ion traps - 3D Printing Industry - March 16th, 2020
- Deltec Bank, Bahamas - Quantum Computing Will have Positive Impacts on Portfolio Optimization, Risk Analysis, Asset Pricing, and Trading Strategies -... - March 16th, 2020
- NIST Works on the Industries of the Future in Buildings from the Past - Nextgov - March 16th, 2020
- Archer Materials" patent application received by World Intellectual Property Organisation - Proactive Investors Australia - March 16th, 2020
- Why the Journey to Cloud Must Start With the Workforce - AiThority - March 9th, 2020
- 'Devs': How the FX on Hulu show's tech compares with reality - Los Angeles Times - March 5th, 2020
- Quantum Computing Market: Qualitative Analysis of the Leading Players and Competitive Industry Scenario, 2025 - Express Journal - March 5th, 2020
- Quantum Computing Market 2019 Analysis by Key Players, Share, Trend, Segmentation and Forecast to 2029 - News Times - March 5th, 2020
- Cracking the uncertainty around quantum computing - Information Age - March 4th, 2020
- Surprise contender Honeywell enters the quantum computing race - New Scientist News - March 4th, 2020

## Recent Comments