Low-loss fiber-optic single-photon buffer

Akiko Tada, Naoto Namekata, Shuichiro Inoue

Akiko Tada, Naoto Namekata, Shuichiro Inoue

We demonstrated an efficient fiber-optic single-photon buffer (SPB) at 1550 nm. The SPB can control and give discrete time delays to a single-photon. Moreover the SPB is passively polarization-stable, and consequently the polarization-based quantum state of light can be maintained. The insertion loss of the SPB is as low as 2.98 dB, which indicates that it can be used for enhancement of efficiencies of heralding single-photon sources and multi-photon interference experiments.

Anna Musiał, Grzegorz Sek, Philipp‐Immanuel Schneider +1 more

Kim Fook Lee, Gamze Gül, Zhao Jim +1 more

Abstract We report a fiber loop quantum buffer based on a low-loss 2 × 2 switch and a unit delay made of a fiber delay line. We characterize the device by using a two-photon polarization entangled state in which one photon of the entangled photon pair is stored and retrieved at a repetition rate up to 78 kHz. The device, which enables integer multiples of a unit delay, can store the qubit state in a unit of fiber delay line up to 5.4 km and the number of loop round-trips up to 3. Furthermore, we configure the device with other active elements to realize integer multiplier and divider of a unit delay of a qubit. The quantum state tomography is performed on the retrieved photon and its entangled photon. We obtain a state fidelity > 94 % with a maximum storage time of 52 μs with an insertion loss of 5.56 dB. To further characterize the storing and retrieving processes of the device, we perform entanglement-assisted quantum process tomography on the buffered qubit state. The process fidelity of the device is > 0.98. Our result implies that the device preserves the superposition and entanglement of a qubit state from a two-photon polarization-entangled state. This is a significant step towards facilitating applications in optical asynchronous transfer mode based quantum networks.

Bahaa E. A. Saleh

Xiaoxi Wang, Shayan Mookherjea

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.