Summary: Quantum supremacy marks the first time a quantum device performed a computation beyond the reach of classical supercomputers. In October 2019, Google’s Sycamore processor ran a random circuit sampling task on 53 qubits in about 200 seconds, an achievement heralded as a new era in computing. IBM researchers later showed classical systems could approximate the same task faster than initially claimed, fueling debates on benchmarks. By December 2020, Chinese teams extended supremacy to photonic systems, underscoring rapid progress in 2019–2020.

What Is Quantum Supremacy?

Quantum supremacy refers to the demonstration that a quantum computer can solve a specific problem that no classical computer can solve in any reasonable time [1]. The term was popularized by John Preskill in 2012 to signify a clear milestone in quantum computing research.

Google’s Sycamore Experiment

In October 2019, Google used its 53‑qubit Sycamore processor, designed as a 2D array of superconducting qubits, to perform random circuit sampling in about 200 seconds [2, 3]. Google estimated that the world’s fastest classical supercomputer would need roughly 10,000 years to replicate the experiment’s output [4]. NASA highlighted how Sycamore’s connectivity and error rates made classical emulation infeasible at that scale [5].

Classical Counterarguments

Shortly after Google’s announcement, IBM researchers demonstrated that, with optimized algorithms and a supercomputer cluster, the same sampling task could be simulated in about 2.5 days [6, 7]. This result underscored that rising classical hardware performance and clever software optimizations can narrow the gap with NISQ devices.

Beyond Superconducting Qubits: Photonic Supremacy

In December 2020, a team led by Pan Jianwei at USTC in China used the Jiuzhang photonic processor to perform Gaussian boson sampling with 76 photons in about 200 seconds [1]. They estimated a classical supercomputer would need around 2.5 billion years for the same task, extending the supremacy milestone beyond superconducting platforms.

Impact and Outlook

The Sycamore and Jiuzhang demonstrations represent key benchmarks for NISQ-era devices [8, 9]. They highlight both the potential and limitations of current quantum hardware: while specialized tasks can now outpace classical machines, error rates and lack of fault tolerance constrain broader applications. Future advances hinge on improved qubit coherence, scalable error correction, and algorithmic breakthroughs to tackle real-world problems.

References

[1] Wikipedia contributors. (2021). Quantum supremacy. Wikipedia. https://en.wikipedia.org/wiki/Quantum_supremacy

[2] Arute, F., et al. (2019). Quantum supremacy using a programmable superconducting processor. Nature, 574(7779), 505-510. https://www.nature.com/articles/s41586-019-1666-5

[3] Google AI Blog. (2019). Quantum Supremacy Using a Programmable Superconducting Processor. https://research.google/blog/quantum-supremacy-using-a-programmable-superconducting-processor/

[4] Vardi, M. Y. (2019). Google’s Quantum Supremacy Claim: What It Means for Computing. Time. https://time.com/5708327/google-quantum-supremacy-explainer/

[5] NASA. (2019). Google and NASA Achieve Quantum Supremacy. https://www.nasa.gov/technology/computing/google-and-nasa-achieve-quantum-supremacy/

[6] IBM Research Blog. (2019). On “Quantum Supremacy”. https://www.ibm.com/quantum/blog/on-quantum-supremacy

[7] Moorhead, P. (2019). Google Claims Quantum Supremacy, IBM Says Nope: Unpacking What’s Important. Forbes. https://www.forbes.com/sites/forrester/2019/10/28/google-claims-quantum-supremacy-ibm-says-nope-unpacking-whats-important/

[8] Conover, E. (2019). Google’s quantum supremacy claim and controversy were top science stories of 2019. Science News. https://www.sciencenews.org/article/google-quantum-supremacy-claim-controversy-top-science-stories-2019-yir

[9] WIRED Staff. (2021). The WIRED Guide to Quantum Computing. WIRED. https://www.wired.com/story/wired-guide-to-quantum-computing