Broadband polarization-entangled system for C+L-band flex-grid quantum networks

A system for distributing entangled-photon pairs for multi-band spectrum, the system comprising:

• a source of entangled-photon pairs, the source comprising a pump laser and a nonlinear medium that are configured and operated to produce, when the pump laser pumps the nonlinear medium, pairs of polarization-entangled frequency-correlated photons having frequencies fi and fii centered on a boundary between two bands of the multi-band spectrum, wherein for any pair of entangled photons, the frequency fi of one is within a band frequency range and the frequency fii of the other one is within another band frequency range, where the frequency of each is equidistant from the boundary;
• beam splitting subsystem in optical communication with the source, the beam splitting subsystem is configured to receive the pairs of polarization-entangled frequency-correlated photons and divide the received polarization-entangled frequency-correlated photons into different optical paths by band;
• a first-band wavelength-selective switch (WSS) positioned in a first path of the different optical paths and configured to receive polarization-entangled frequency-correlated photons in a first band, the first-band WSS having Mff distribution ports;
• an second-band WSS positioned in a second path of the different optical paths, and configured to receive polarization-entangled frequency-correlated photons in a second band, the second-band WSS having Mss distribution ports, wherein the photons entering the first-band WSS are grouped by frequency into N channels of δf-width bins aligned to the ITU grid for control and photons entering the second-band WSS are grouped by frequency into O channels of δf-width bins aligned to the ITU grid for control, where N≥Mff and 0≥Mss, wherein the first-band WSS's jth channel associated with a channel frequency fij is controllable concurrently with the second-band WSS's jth channel associated with a channel frequency fiij, for channel frequencies that are equidistant from the boundary, where j=1, . . . , N;
• and
• a network controller having one or more communication interfaces, the network controller communicatively coupled with the first-band WSS and the second-band WSS and receivers, the network controller configured to
• receive a request to provide to first and second optical receivers respective photons of entangled photon pairs, wherein the first optical receiver is coupled through an optical communications network to the first-band WSS's
• a
• w
• th
• distribution port and the second optical receiver is coupled through the optical communications network to the second-band WSS's
• a
• x
• th
• distribution port, where aw=1, . . . , Mff and ax=1, . . . , Mss,
• determine if there is available bandwidth to satisfy the request, and
• cause the first-band WSS to connect the first-band WSS's jth channel to the first-band WSS's
• a
• w
• th
• distribution port and the second-band WSS to connect the second-band WSS's jth channel to the second-band WSS's
• a
• x
• th
• distribution port when there is available bandwidth to cause a distribution of photons of entangled-photon pairs to the first and second optical receivers.