Quantum advantage or quantum supremacy - what is the difference?

Author:Jukka Knuutinen
Expert contributor:Dr. Valtteri Lahtinen
QUANTUM COMPUTING -️ May 17, 2022

Quantum advantage and quantum supremacy are words often thrown around, but what exactly do they mean, and what is the difference between them?

On the surface level, this seems like an easy enough question to just google; however, as one will soon thereafter see, there is a lot of contradicting information online when it comes to defining these terms.

This article aims to shed light on these questions and straighten out some of the misconceptions. At the least, as there are no absolute truths in defining words, we are stating our policy for the usage of these terms in previous and upcoming blog articles and other communications.

Quantum supremacy vs. quantum advantage

Google made headlines in 2019 when they announced that they had achieved quantum supremacy with their 53-qubit sycamore processor.

In their demonstration, Google's quantum computer solved a problem that, as per their statement, would take a modern supercomputer 10 000 years* to solve.

*Google's claim was challenged by IBM, stating that by using better algorithms, a modern supercomputer could, in fact, solve the same problem in a reasonable amount of time.

In 2020 Chinese researchers announced that they had achieved quantum advantage by performing computations on a quantum device that would be mathematically impossible to perform using classical computers.

What are the definitions?

Quantum supremacy refers to quantum computers solving tasks that are impossible for classical computers in any reasonable time. This is precisely what Google did in 2019.

What was achieved in China was not much different. They also solved a task that is impossible for classical computers, but a task that is in not of practical importance and therefore, as one might say, gives no advantage.

Quantum advantage refers to quantum computers solving tasks that have practical usage, for example, problems stemming from physics or economics.

This does not require the solving to be commercially viable, though, as the current expenses of running and maintaining a quantum computer might largely exceed the value it may bring.

The term useful quantum advantage or even commercially useful quantum advantage might be used for commercially viable benefits.

What we do

The simulations that we can run with our software here at Quanscient help companies build the required technology to achieve commercial quantum advantage.

Furthermore, the quantum algorithms we are developing will also aid in achieving useful quantum advantage, granted, depending on the hardware development.

Controversy

The term quantum supremacy has stirred up some discussion stemming from the word's negative connotations.

Quanscient does not take part in the discussion of what the appropriate term might be, only the fact that when it comes to celebrating the achievements of quantum computers solving problems classical computers cannot, it is essential to differentiate the nature of the problems between practical and impractical.

For the time being and the lack of a better alternative, we will use the aforementioned terms to differentiate between these two.

Conclusion

  • Although the definitions for quantum supremacy and quantum advantage have gotten mixed up and blurry, it is important to differentiate between the two.
  • Quanscient will use quantum advantage to refer to speed-ups in practical applications.
  • Our research and software are making it possible to reach commercial quantum advantage.