# Realizing quantum computing

Prof. Foluso Ladeinde

For many applications, the computer seems to be fast enough.

Afterall when you ask it to search the web for some information, it usually comes back with the results within seconds. And chances are that you are doing this with just one core of the CPU (Central Processing Unit) in your desktop or smartphone.

However, for many scientific applications, a single core in your computer will not be sufficient, as it could take many years to get the results back from the computer after you assign it a task. This is the reason why we have supercomputers. The world’s most powerful supercomputer contains the equivalence of over three million (3,000,000) single-core desktop computers. Unfortunately, we still cannot carry out some computations in good time even when we use these supercomputers. This is the reason why many organizations – currently high-tech ones – have gone out in full force in search of quantum computers (QCs). Such companies include IBM, Google, Microsoft, and Intel. According to Ben Fox Rubin of ZDNet.com, “IBM has partnered with ExxonMobil, Daimler, Samsung, Barclays and major corporations to kick the tires on what’s possible with its quantum computers.”

Last week Thursday (18 June 2020), Honeywell, an American high-tech company, announced that it has built the world’s most powerful QC, which is at least twice as powerful as the existing QCs operated by IBM and Google. Honeywell’s machine has reportedly achieved a Quantum Volume (QV) of 64. (Quantum Volume is a performance metric devised by IBM that measures the capability of quantum machines and error rates.) By comparison, IBM announced in January 2020 that it had obtained a QV of 32 with its latest quantum machine. In October 2019, Google announced that it had developed a quantum machine which took 200 seconds (less than 4 minutes) to complete a calculation that would otherwise have taken a supercomputer 10,000 years. However, IBM reportedly disputed Google’s claim, contending that the said calculation would have taken only 2.5 days to complete.

A quantum computer differs from our everyday computer in several aspects, which was presented in this column on 22 June 2015, and from which the descriptions below have been taken almost verbatim. The traditional computer does everything in terms of ones and zeroes. Thus, we have two, or binary, states: 0 and 1 (or logically “off” and “on”). Instructions and the data they operate on, must eventually be converted to strings of 0’s and 1’s. The conversion of decimal data to the binary system is an exercise for a secondary school student.

Quantum computing uses the laws of quantum mechanics in physics to process information. A QC uses quantum bits, abbreviated “qubits,” which is a system that encodes the one and the two into two distinguishable quantum states. However, quantum particles behave “randomly” (stochastically or probabilistically, in grown-up’s terminologies). Therefore, we can exploit the fact that a quantum system can be in multiple states at the same time. In other words, something can be “here” and “there,” or “up” and “down” at the same time, in the words of the Institute of Quantum Computing (IQC) at the University of Waterloo in Canada. The ability of a quantum system to be in multiple states at the same time is referred to as superposition.

The existence of an extremely strong correlation between quantum particles is also exploited in QC. That is, two quantum particles remember each other’s locations in space and time, no matter the distance of separation – even when placed at opposite sides of the universe! This connection which, by the way, boggles the mind, is referred to as entanglement. Thus, the superposition and entanglement phenomena enable a QC to process an inordinately huge number of calculations simultaneously, compared to just one at a time for traditional computers. However, coming up with the algorithms that exploit these features is a challenge.

The list of possibilities with QCs relative to traditional computers is long. The use in cryptography is particularly noteworthy. While any computer can multiply two large numbers, breaking a large number (say with 500 digits) into its factors is presently only in the (potential) purview of QCs. Encryption technologies exploit the difficulty of using traditional computers to factor large numbers. According to IQC, “In fact, the difficulty of factoring big numbers is the basis for much of our present-day cryptography. It’s based on mathematical problems that are too tough to solve. RSA (Rivest-Shamir-Adleman) encryption, the method used to encrypt your credit/ATM card number when you shop online, relies completely on the factoring problem.”

Besides the potential use in encryption, QC has the ability to accurately simulate physics at the atomic level, which could speed up the rate at which drugs are developed and provide better ways of removing carbon dioxide from the atmosphere. Image and face recognition technologies, as well as the ability to handle big data, are other highly attractive promises of QC. However, QC is not cure-all! As pointed out by The UK Economist magazine several years ago, compared to traditional computing, downloading web pages will not go faster with QC, nor will QC enhance graphics processing in computer games. Hardcore scientific simulations are where QC would find worthy application.