A significant advancement in quantum computing using a photonic processor is Borealis. This processor demonstrates quantum computational advantage by outperforming classical computers in specific tasks. Borealis achieves this through dynamic programmability of all its quantum gates, a feature not previously available in photonic machines. It employs Gaussian boson sampling on 216 squeezed modes with three-dimensional connectivity, using a time-multiplexed and photon-number-resolving architecture​​.
Key highlights from the article include:
Quantum Computational Advantage: Borealis marks a milestone by showing quantum computational advantage, a feat where quantum devices perform tasks beyond the reach of classical computers. This is achieved in tasks that involve sampling from probability distributions that are hard to simulate classically​​.
Time-Domain Multiplexing: The photonic processor uses time-domain multiplexing, which is efficient for building fault-tolerant quantum computers. This method encodes quantum information in sequential light pulses, allowing large and highly entangled states to be processed with a small number of optical components​​.
Technical Innovations: Borealis addresses challenges in time-domain multiplexing, fast electro-optical switching, and high-speed photon-number-resolving detection. It can synthesize a 216-mode state with a three-dimensional entanglement topology, a significant step towards practical quantum computing​​.
Experiment Details: The experiment involves a fully programmable optical circuit that synthesizes a multimode entangled Gaussian state. This is achieved using variable beamsplitters and phase-stabilized fiber loops, allowing interference between modes that are temporally adjacent or separated by specific time bins​​.
Performance Metrics: In terms of performance, it is estimated that the Fugaku supercomputer would take about 9,000 years to generate one sample from the programmed distribution, while Borealis does it in only 36 microseconds. This performance is orders of magnitude faster than earlier photonic machines​​.
Advantages over Previous Demonstrations: Borealis stands out from previous demonstrations in its dynamic programmability, photon-number-resolved detection, and a reduced number of required optical components. It uses the largest number of independent quantum systems in such demonstrations, being more resistant to classical spoofing attacks​​.