Silicone Photonics and Quantum Computing

Silicon photonics—which leverages mature semiconductor fabrication to create complex circuity for light—is poised to revolutionize a range of modern classical and quantum optical device physics, from coherent communications to novel architectures for quantum photonic circuits. Technologies that once required sizeable free-space or fiber-optic systems now have the potential to be chip-scale: low-cost, robust, and scalable in ways that weren’t possible before. At the same time, exquisite control of nano-scale structures and tight confinement of light—readily achieved in these integrated systems—enable a new array of device physics based on radically enhanced light-matter interactions. Light-sound interactions, known as stimulated Brillouin scattering, can be harnessed to address long-standing challenges in silicon photonics and to enable the design and production of silicon-based lasers, amplifiers, and isolators. Moreover, these advances unveil intriguing new optical physics, allowing the study of extreme regimes of three-wave laser dynamics and, for the first time, laser cooling of propagating sound waves. It harnesses intermodal Kerr-based nonlinearities to achieve quantum frequency conversion over large (> 1 octave) wavelength shifts as the basis for flexible, room-temperature quantum silicon photonics. This new capability enables enhanced (> 25× stronger) nonlinearities for state-of-the-art quantum information processing and sensing technologies. It allows a new class of robust, room-temperature infrared single-photon detectors, and is an essential step toward frequency-agnostic quantum networking for next-generation hybrid quantum systems. 

It can perform two distinct, independent operations simultaneously on two qubits encoded on photons of different frequencies. Qubits are the smallest unit of quantum information. Allowing the realization of universal quantum computing, you need to be able to do other operations on different qubits simultaneously—different quantum gates in parallel on two entangled frequency-bin qubits in the optical fiber. The quantum frequency processor allowed it to manipulate the frequency of the photons to bring about superposition, the state that enables quantum computers to perform operations concurrently. Controlling the spectral overlap between adjacent spectral bins, observe frequency-bin interference, and demonstrate 97 percent interference visibility. It is integrating this tunability with frequency parallelization to synthesize independent gates on entangled qubits. It enables Bayesian inference — a statistical method associated with machine learning — to confirm that the operations on the quantum processor were done with high fidelity and with absolute control.

“A lot of researchers are talking about quantum information processing with photons, and even using frequency,” researcher Joseph Lukens said. “But no one had thought about sending multiple photons through the same fiber-optic strand, in the same space, and operating on them differently.”