Quantum Supremacy

by Waree Sethapun ’20

Late in September of 2019, a research paper titled “Quantum Supremacy Using a Programmable Superconducting Processor,” was briefly posted on a NASA website before being taken down. The author being “Google AI Quantum and collaborators.” In the abstract of this paper, which is still circulating the internet, Google claims to have provided “an experimental realization of quantum supremacy on a computational task.” The keyword that struck mass hysteria is quantum supremacy: the outperformance of quantum computers over their classical counterparts. Does this mean that we are finally at an age of quantum computers taking over classical computers? 

First, a quick recap on the current state of quantum computing. A quantum computer uses qubits (quantum bits) instead of the classical binary bits used in devices today. Qubits are advantageous in solving specific problems due to their quantum property of superposition: the ability to exist in many states at the same time. Quantum computers were envisioned by physicists in the 1980’s and since then, bits and pieces of knowledge and technology, such as quantum algorithms and semiconductor chips, came together to pave the way for a realization that quantum computers might actually be technologically feasible. As what MIT professor, Isaac Chuang said, “It is no longer a physicist’s dream—it is an engineer’s nightmare.” In the 2010’s, many labs and universities starting to specialize in quantum computation, and companies saw commercial potential in this too. During these past few years, IBM, Google and Intel have all attempted to engineer quantum processors in an effort to reach quantum supremacy.

A law that points out that the remarkable rate at which technology improves is due to the Moore’s Law: the number of transistors on a chip doubles every two years, leading to the increase of computing power year after year. Moore’s Law has been surprisingly accurate for almost five decades, but it has begun to plateau. The components on a chip are getting packed so tightly together as to approach the physical limit. On the other hand, quantum technology has advanced so much that there is a similar law in place: Neven’s Law. Neven’s Law suggests that we should reach quantum supremacy in 2019, and here we are.

So, what did Google do to achieve quantum supremacy? From Google’s paper, they used their processor named Sycamore “…a processor with programmable superconducting qubits to create quantum states … While our processor takes about 200 seconds to sample one instance of the quantum circuit 1 million times, a state-of-the-art supercomputer would require approximately 10,000 years to perform the equivalent task.” The task being to prove that numbers produced by a random number generator were truly random. Though this task has little practical application, it paves the way for solving other problems classical computers could not handle and the results can be extraordinary. 

Google was able to demonstrate quantum supremacy – but for a very narrow task. There are still a myriad of problems facing quantum computers such as their need for an isolated operating environment and their inability to maintain quantum states for long periods of time. This means that quantum computers are not going to take over yet, and they may never replace our everyday laptops in terms of normal use. There are some tasks classical computers are more suited to handle as there are tasks quantum computers are more suited to handle. The underlying philosophy is that quantum computers are not meant to do the same old things in a different way, but they are rather meant to solve problems that we cannot even comprehend in a new way. The advances in technology are getting us closer, qubit by qubit.

Sources:

Cho, A. (2019, September 27). Google claims quantum computing milestone. Retrieved from https://science.sciencemag.org/content/365/6460/1364.

Giles, M. (2019, September 25). Here’s what quantum supremacy does-and doesn’t-mean for computing. Retrieved from https://www.technologyreview.com/s/614423/quantum-computing-and-quantum-supremacy/.

Hartnett, K. (2019, June 21). A New “Law” Suggests Quantum Supremacy Could Happen This Year. Retrieved from https://www.scientificamerican.com/article/a-new-law-suggests-quantum-supremacy-could-happen-this-year/