Nitin Jain, Northwestern University
Quantum-optical frequency conversion (QFC) provides a method, usually via a nonlinear interaction with an optical ‘pump’ beam, to keep the quantum features of an optical ‘signal’ intact. Most QFC experiments
upconvert near-infrared signal photons to those in the visible or near-visible regime due to the availability of highly-efficient detectors that can be operated at high speeds without incurring a severe noise penalty.
Such upconversion based senders/receivers can therefore enable quantum communication at large throughputs. If the pump pulses inside an upconversion receiver (Bob) are carefully designed, it can permit Bob to also define and control the modes that participate in the quantum measurement. This can be employed to restrict the degrees of freedom which an eavesdropper (Eve) might otherwise exploit to take advantage of the imperfections of the detection apparatus in a practical quantum key distribution (QKD) system. Moreover, by manipulating and monitoring the characteristics of the pump pulses, Bob can also detect a wide range of Eve’s attacks, such as those inflicted by laser damage, faked states, etc. Such upconversion receivers can therefore enhance the security of practical QKD systems.
In my talk, I shall discuss our recent efforts to implement multidimensional, high-speed upconversion based systems. I shall also detail a novel upconversion receiver design that can protect Bob against various quantum hacking attacks.