Budget entanglement: a compact and intrinsically stable source of polarization entangled photons

Quantum theory predicts the existence of entanglement, a bizarre and counterintuitive property that some once viewed as being incompatible with any "reasonable definition of reality" [1]. Experimental results, such as tests of Bell inequalities [2], have since shown that entanglement is not merely a mystery of quantum theory, but also, a resource that exists, can be observed, and can be exploited to expand the realm of what is possible in fields such as computation and communication. In this talk we will present a novel source of entanglement and some experimental results of its characterization. This inexpensive, compact, and robust source produces polarization entangled photon pairs at non-degenerate wavelengths of 810 nm and 1550 nm, uses commercially available non-linear crystals configured in a Sagnac interferometer, and is pumped by an inexpensive laser pointer. It requires no active stabilization and produces uncorrected entanglement visibilities exceeding 96%. This source shows great promise for future applications in practical systems as well as for use in testing Bell inequalities that require high visibility sources [3]. 1. A. Einstein, B. Podolsky, N. Rosen, "Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?", Physical Review 47 , 777-780, 1935 2. A. Aspect, "Bell's inequality test: more ideal than ever", Nature, 398, 189-190, 1999. 3. N. Brunner, N. Gisin, "Partial list of Bell inequalities with four binary settings", Phys. Rev. A. 372, 3162-3167, 2008.