High Speed Low Loss Quantum Optical Switch for 1550nm band

Optical switches that are simultaneously fast (sub-nanosecond), low loss (< 2 dB), and add low noise (< 10-4 added noise photons per mode) are not available commercially, but would be an important tool for manipulating quantum signals. It is important for such a switch to operate near 1550 nm, as this is the lowest loss wavelength in standard optical fibers and as such is desirable for distributing quantum information over long distances. Switches based on cross-phase modulation in optical fiber are capable of meeting the requirements, but have thus far for technological reasons operated near 1310 nm. We will develop new optical switches suitable for quantum signals in the 1550 nm band. Various components of the switch will be characterized to optimize the design, and the switching function will be demonstrated. Since the proposed switch geometry is essentially a long interferometer, an active phase locking scheme will be developed to enable stable and reliable operation. The locking scheme will be extended to allow for multiple cascaded interferometers which enables more complex optical processing. We will demonstrate the ability of the switch to maintain signal fidelity when operating on a quantum entangled signal, thereby showing the feasibility of the technology.