Quantum Imaging Lab at Boston University

The development of nonclassical sources of light that rely on the quantum nature of the electromagnetic field has proceeded apace in the past decade. Generically referred to as quiet light, these quantum sources exhibit reduced fluctuations (noise) in comparison with classical sources such as natural light, and light from LEDs and lasers. A particularly useful quantum source of light is the entangled photon state, which may be generated by spontaneous optical parametric downconversion (SPDC). In this process, a laser beam illuminates an anisotropic nonlinear crystal oriented at the proper angle. A photon from the pump laser (the "mother photon") is split into a pair of twins (the "daughter photons"). The energy and momentum of the mother are shared by the daughters, which share entanglement by virtue of the nonseparability of the quantum state that describes them. It is the mission of the Quantum Imaging Laboratory to exploit nonclassical light for the purposes of optical imaging, communications, cryptography, teleportation, and computing.