Single-photon measurements of an electro-optic silicon-photonic add-drop microresonator demonstrate entanglement-preserving voltage-driven switching with fast 10%-90% transition times [<50 ps], low-loss transmission [94% (90%) bar (cross)-state] and high quantum two-photon interference visibility [~99%] at 1550 nm.
A high-speed, low-loss modular cross-bar switching element suitable for single photons is demonstrated. Entanglement preserving voltage-driven switching of single photons is achieved with a unique combination of ultra-fast and low-loss characteristics (less than 50 ps 10%–90% transition time and greater than 90% transmission), and we present a roadmap towards even lower losses. The switch properties are well matched to the wavelength, bandwidth and lifetime of photons generated by spontaneous four-wave mixing sources also realized in silicon photonics. Such a switch can enable reconfigurability of each single photon and addressing of each time bin, and benefit future quantum photonic circuits.
Efficient single-photon routing and switching are crucial for optical quantum computing and communication. For this purpose, all-optical switches are designed for gigahertz bandwidths. The switching mechanism is based on the optical Kerr effect via cross-phase modulation (CPM) of the single-photon signal by a strong 1550-nm pump pulse. For energy-efficient switching, this nonlinear effect is exploited in a microresonator that can either be used directly as an intensity switch in a typical add–drop configuration or as a phase shifter in a Mach–Zehnder interferometer (MZI) structure. To speed up resonance build-up and quenching, a pre-emphasis build and an off-resonance wipe pulse are used. The proposed designs are verified by traveling-wave simulations which demonstrate that 0.1 dB insertion loss and ~1 ns switching windows can be achieved. For a scalable out-of-the-lab transfer, we investigate the feasibility of the proposed switch designs for fabrication in a mature photonic integrated circuit (PIC) platform. In particular, silicon nitride PICs have demonstrated record-low losses which makes them suitable for single-photon applications. By parametric modelling of the microresonator’s directional couplers based on Lumerical EME and 2.5-dimensional varFDTD simulations, the required power transmission coefficients for both signal and pump wavelength can be achieved. This results in an all-optical switch design ready for fabrication in a commercial PIC foundry which can potentially enable scalable architectures for quantum photonic applications.
As the field of quantum communications matures and adopts larger network topologies, it will require switches capable of multiplexing and demultiplexing entangled photons between network nodes. Such switches will need to operate at high speeds, with low loss, and minimal signal-band noise, while also retaining the quantum state of the routed photons. We present an all-optical, fiber-based, dual-in, dual-out switch that has a switching window of 45 ps and an insertion loss of <;3.0 dB. In addition, the switch introduces minimal degradation to the quantum state of the routed entangled photons. As a test of the switch's utility, we demultiplex a single quantum channel from a 6.5-GHz dual-channel quantum data stream. The recovered quantum state exhibits a fidelity of 96.2%±1.2% with the prepared state.
A strategy for realizing a microchip-scale single-photon digital loop buffer controlled by low-voltage electronic signals was studied in the context of integrated photonics. A potential implementation for bridging a gap between other technologies used a recirculating loop architecture based on advances in low-loss passive waveguides and a fast electro-optic add-drop switch. Although the requirements of single-photon buffers are demanding, our analysis suggested that a voltage-controlled, room-temperature catch-and-store short-term quantum memory for light on a chip may be feasible in certain regimes.