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Critical Topics and Their Significance for the UPSC CSE Examination on April 09, 2025

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Scientists demonstrate clear quantum advantage using simple game

For Preliminary Examination:  Current events of national and international Significance

For Mains Examination: GS III - Science & Technology

Context:

Previous attempts at showing quantum supremacy have used complicated problems. Google used random circuit sampling for its Sycamore processor, andChinese researchers used the Gaussian boson sampling problem for the Jiuzhang computer. Both require specialised equipment to perform, making it difficult to verify the results

Read about:

National Quantum Computing Mission

Quantum Computer

Key takeaways:

• For years, scientists have been seeking a task where quantum computers outperform classical computers, a benchmark known as quantum supremacy.
• Recently, researchers from the University of Oxford and Universidad de Sevilla achieved this milestone using a relatively simple game-based approach. Their findings, published in Physical Review Letters in February, are based on a problem involving odd-cycle graphs.
• The challenge is to colour a circle with an odd number of points using only two colours in such a way that no two adjacent points share the same colour—an outcome that is mathematically impossible.
• The researchers turned this puzzle into a test for quantum supremacy, moving away from earlier, more complex demonstrations. For instance, Google used a task known as random circuit sampling to demonstrate its Sycamore processor’s capabilities in 2019, while Chinese researchers employed Gaussian boson sampling on the Jiuzhang quantum computer. These methods, however, require intricate math and specialised tools, making external validation difficult.

The Colouring Challenge

• In the adapted experiment, the odd-cycle graph problem is used in a game format. Imagine a circle with three points—trying to colour them using only red and blue such that adjacent points don’t match will always lead to a contradiction.
• In this game, two players, Alice and Bob, who cannot communicate, respond to questions from a referee about the colours of points on the circle. To win, their responses must meet two criteria: they must give the same answer for the same point, and different answers for adjacent points.
• In a classical scenario, even with an agreed strategy beforehand, the best possible win rate for a 3-point circle is 83.3%.

Quantum Implementation