In the race to create a quantum computer that can outperform a classical one, a method using particles of light (photons) has taken a promising step forward. Jian-Wei Pan and Chao-Yang Lu, both at the University of Science and Technology of China, and their colleagues improved a quantum computing technique called boson sampling to achieve a record 14 detected photons in its final results. Previous experiments were capped at only five detected photons. The increase in the number of the particles is small, but it amounts to a 6.5-billion-fold gain in “state space,” or the number of ways in which a computer system can be configured. The larger the state space, the less likely a classical computer can perform the same calculation.
The result was reported in a paper posted at the preprint server arXiv.org on October 22 and has yet to be peer-reviewed. But if it is confirmed, it would be an important milestone in the race for quantum-computational supremacy—a fuzzy goalpost defined as the point where quantum computers outpace their best classical counterparts.
In classical computers, information is encoded in binary bits, so two bits could be 00, 01, 10 or 11. A quantum computer can be in every classical state simultaneously: two qubits have some probability of being 00, 01, 10 and 11 until they are measured; three qubits have a probability of being in any of eight states; and so on. This exponential increase in information illustrates why quantum computers have such an advantage—in theory.
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