Systems for generating, manipulating, and measuring entangled photons are described. Quantum state tomographies are recorded with one of the entangled photons distributed over fiber. A high speed, low loss quantum switch for 1550 nm photons is demonstrated, which can manipulate photons for processing or multiplexing.
We report on a system for the generation and measurement of polarization entangled photons. High speed quantum state tomographies with a raw fidelity of >; 91 % with respect to an ideal entangled state are recorded in <; 2 seconds, with longer-term accidental-count subtracted fidelities exceeding 99%. Two-photon interference measurements are recorded using an automated alignment and measurement procedure with the signal distributed over 20 km of fiber. These high speed measurement methods are useful for high rate monitoring of entangled states.
The development of high-quality photonic sources of high-dimensional entanglement and techniques for their manipulation is crucial for the advancement of quantum technologies. We present an efficient technique for generating and characterizing high-dimensional spatially entangled two-photon states with a record quality, dimensionality, and measurement speed. We demonstrate how to precisely manipulate such states by tailoring reprogrammable optical circuits in complex scattering media consisting of off-the-shelf multimode fiber and spatial light modulation. Our techniques open a clear pathway for the adoption of high-dimensional quantum states of light in the high-capacity, noise-robust quantum networks of tomorrow.
Quantum signals such as entangled photons are typically at the sub-photon level and, thus, require near noise-less and low-loss components for their manipulation and processing. A common signal-manipulation tool is a 2 × 2 switch, and many applications of quantum switches also require fast switching rates and input signals in the fiber-friendly 1550-nm band. Traditional optical switching technology does not simultaneously meet all the desired metrics for a quantum switch. We demonstrate a low-noise fiber-optic photonic switch based on cross phase modulation that is fast (sub-ns), low loss (<;1 dB), and operates in the 1550-nm wavelength band.