A system includes a quantum light device comprising a light source configured to emit a plurality of pairs of photons, wherein each pair of photons of the plurality of pairs of photons occupies a quantum entangled state. The system also includes optical circuitry configured to receive a first set of photons and a second set of photons. A set of photon detectors may receive the first set of photons and the second set of photons from the optical circuitry. Additionally, the system may include processing cirucitry configured to determine, based on a set of time signals corresponding to each photon detector of the set of photon detectors, whether a time delay value exists in which a Clauser, Home, Shimony and Holt (CHSH) parameter is greater than a threshold CHSH parameter value.

A nanostructure controlling a single photon which controls both of the position and the polarization direction of a single photon is proposed. An embodiment is a nanostructure controlling a single photon which includes a substrate and at least one insulating film units having a first insulating film and a second insulating film spaced apart from each other on the substrate and in which the portion between the first insulating film and the second insulating film is defined as a first nanogap.

A nanostructure controlling a single photon which controls both of the position and the polarization direction of a single photon is proposed. An embodiment is a nanostructure controlling a single photon which includes a substrate and at least one insulating film units having a first insulating film and a second insulating film spaced apart from each other on the substrate and in which the portion between the first insulating film and the second insulating film is defined as a first nanogap.

A photon entanglement system is disclosed which includes a plurality of remote nodes (Nodes A.sub.i and Node B.sub.i) each without a quantum memory; and a central entangling node (Node C) in both quantum and classical communication with the remote Nodes configured to provide photon entanglement therebetween, and includes a first and second broadband photon generators each adapted to generate sets of photon pairs at: i) random times within time-bins, and ii) random frequency bins, wherein one photon of each pair set is transmitted to an associated remote node over quantum channels, and a multiplexed Bell-state analyzer configured to receive another photon of the pair, wherein if the received photons arrive at about same time, then the received photons are marked as being entangled by the controller which communicates the associated time-bin to the associated remote nodes and thereby entangling their associated photons.

A photon entanglement system is disclosed which includes a plurality of remote nodes (Nodes A.sub.i and Node B.sub.i) each without a quantum memory; and a central entangling node (Node C) in both quantum and classical communication with the remote Nodes configured to provide photon entanglement therebetween, and includes a first and second broadband photon generators each adapted to generate sets of photon pairs at: i) random times within time-bins, and ii) random frequency bins, wherein one photon of each pair set is transmitted to an associated remote node over quantum channels, and a multiplexed Bell-state analyzer configured to receive another photon of the pair, wherein if the received photons arrive at about same time, then the received photons are marked as being entangled by the controller which communicates the associated time-bin to the associated remote nodes and thereby entangling their associated photons.

A system and method are provided to enable non-quantum experts to schematically represent, simulate and quantify the performance of physically realistic photonic quantum circuits. The framework offers the flexibility for users—not necessarily familiar with the fundamentals of quantum mechanics—to create circuits and work with simple inputs and outputs, while the complexities of manipulating high dimensionality quantum Hilbert spaces supporting photonic and physical quantum object states are handled with the use of purpose-built tools. The tools include a user-friendly method for defining classical photonic circuits which may be coupled to physical objects such as qubits, quantum input states, as well as classical and quantum measurement devices. The tools feature classical-to-quantum S-matrix conversion, quantum S-matrix extraction, as well as capabilities for defining and extracting quantum error parameters. The framework also supports extraction of post-measurement quantum states for use in subsequent circuits or simulators.

A system and method are provided to enable non-quantum experts to schematically represent, simulate and quantify the performance of physically realistic photonic quantum circuits. The framework offers the flexibility for users—not necessarily familiar with the fundamentals of quantum mechanics—to create circuits and work with simple inputs and outputs, while the complexities of manipulating high dimensionality quantum Hilbert spaces supporting photonic and physical quantum object states are handled with the use of purpose-built tools. The tools include a user-friendly method for defining classical photonic circuits which may be coupled to physical objects such as qubits, quantum input states, as well as classical and quantum measurement devices. The tools feature classical-to-quantum S-matrix conversion, quantum S-matrix extraction, as well as capabilities for defining and extracting quantum error parameters. The framework also supports extraction of post-measurement quantum states for use in subsequent circuits or simulators.

Methods, apparatus, and systems are provided for performing a quantum key distribution (QKD) protocol between a first device, a second device, and an intermediary device. The intermediary device transmitting: a first secret symbol string over a first quantum channel to the first device; a first basis set over a first communication channel to the first device. The intermediary device; a second secret symbol string over a second quantum channel to the second device; a second basis set over a second communication channel to the second device. The intermediary device generating a third symbol string based on combining the first and second secret symbol strings and transmitting to the second device, via the second communication channel, data representative of the third symbol string. The first device and second device perform a quantum key exchange and sifting based on the corresponding received first and second secret symbol strings and first and second basis sets, and a fourth set of symbols generated by the second device generates a fourth set of symbols based on combining the second received secret symbols with the received third symbol string.

An emitter configured to output a sequence of periodic light pulses with different polarisations, the emitter comprising:

a beam splitter configured to divide the pulses of a first sequence of pulses, such that each pulse is split between a first path and a second path, the first sequence of pulses having a varying phase and a first polarisation;

a polarisation rotator configured to rotate the polarisation state of pulses in one of the first path or the second path with respect to the polarisation state of pulses in the other path;

a time delay component configured to provide a time delay such that the first sequence of pulses in the first arm are delayed by one period with respect to the first sequence of pulses in the second arm;

an optical combination component configured to combine the delayed first sequence of pulses from the first path with the first sequence of pulses from the second path to produce an output sequence of pulses where each pulse in the output sequence is a combination of a pulse from the second path and a delayed pulse from the first path and has a polarisation determined from the phase difference between combined pulses and the polarisation of the first path and the second path.

An emitter configured to output a sequence of periodic light pulses with different polarisations, the emitter comprising:

a beam splitter configured to divide the pulses of a first sequence of pulses, such that each pulse is split between a first path and a second path, the first sequence of pulses having a varying phase and a first polarisation;

a polarisation rotator configured to rotate the polarisation state of pulses in one of the first path or the second path with respect to the polarisation state of pulses in the other path;

a time delay component configured to provide a time delay such that the first sequence of pulses in the first arm are delayed by one period with respect to the first sequence of pulses in the second arm;

an optical combination component configured to combine the delayed first sequence of pulses from the first path with the first sequence of pulses from the second path to produce an output sequence of pulses where each pulse in the output sequence is a combination of a pulse from the second path and a delayed pulse from the first path and has a polarisation determined from the phase difference between combined pulses and the polarisation of the first path and the second path.