Polarization-independent single-photon switch based on a fiber-optical Sagnac interferometer for quantum communication networks

Abstract

An essential component of future quantum networks is an optical switch capable of dynamically routing single photons. Here we implement such a switch, based on a fiber-optical Sagnac interferometer design. The routing is implemented with a pair of fast electro-optical telecom phase modulators placed inside the Sagnac loop, such that each modulator acts on an orthogonal polarization component of the single photons, in order to yield polarization-independent capability that is crucial for several applications. We obtain an average extinction ratio of more than 19 dB between both outputs of the switch. Our experiment is built exclusively with commercial off-the-shelf components, thus allowing direct compatibility with current optical communication systems.

A tunable quantum random number generator based on a fiber-optical Sagnac interferometer

“…dampened tables, environmental protection, etc) [18] or active stabilization [19,20]. In our work we follow the approach of [8] where we employ a Sagnac interferometer to provide the same functionality, with the added benefit of intrinsic phase stability.…”

“…At the output of the Sagnac loop, we use a 150 meter fiber-optic delay line (L T B ) to add ≈ 750 ns of delay to one term, effectively time-bin multiplexing the two outputs from the Sagnac interferometer into an early and a late time-bin for detection using one single-photon detector. direction and not in the opposing one, thus creating the necessary relative phase shift to generate the different output probabilities in the interferometer outputs [8]. Not shown in figure 2 are two manual polarization controllers added in the Sagnac loop, where one is used to align the pulses' polarization with the input polarization of the phase modulator, while the second one is used to ensure that the two counter-propagating terms have the same polarization at the recombining beamsplitter.…”

“…In this article, we demonstrate a tunable-ratio branching-path photonic QRNG by implementing a dynamically tunable beamsplitter using a fiber-optical Sagnac interferometer. The tunable beamsplitting function is implemented with an active phase modulator placed in a Sagnac loop working as a single-photon router [8]. By modulating the phase of a light packet propagating in the clockwise direction vs the counter-clockwise one, we are able to tune the output probabilities from the Sagnac interferometer through a change in the amplitude of the driving signal fed to the phase modulator.…”

A tunable quantum random number generator based on a fiber-optical Sagnac interferometer

“…In this article, we demonstrate a tunable-ratio branchingpath photonic QRNG by implementing a dynamically tunable beamsplitter using a fiber-optical Sagnac interferometer. The tunable beamsplitting function is implemented with an active phase modulator placed in a Sagnac loop working as a single-photon router [8]. By modulating the phase of a light packet propagating in the clockwise direction vs the counterclockwise one, we are able to tune the output probabilities from the Sagnac interferometer through a change in the amplitude of the driving signal fed to the phase modulator.…”

Post-Measurement Adjustment of the Coincidence Window in Quantum Optics Experiments

“…On the other hand, low-cost architectures based on logic gates (combinational coincidence evaluation) have been proposed as coincidence counters by reducing τ to few tens of nanoseconds [13], then improving to sub nanosecond resolution using external circuits [14]. FPGAs using sequential architectures are capable to acquire and transmit electronic signals in the nanosecond regime [15]- [17], integrating arithmetic processes, and providing flow control over different clocks within a single integrated circuit (IC) [18], [19], even being used to manage different quantum information systems, such as quantum routing [20], [21], quantum random generation [22], [23], and quantum key distribution [24]- [26].…”