Abstract
We present a source of near-infrared photon pairs based on the process of spontaneous parametric downconversion (SPDC), for which the joint signal-idler quantum state is designed to be factorable in the frequency-time and in the transverse position-momentum degrees of freedom. Our technique is based on the use of a broadband pump and vector group velocity matching between the pump, signal, and idler waves. We show experimentally that a source based on this technique can be configured for the generation of: i) pure heralded single photons, and ii) polarization-entangled photon pairs which are free from spectral correlations, in both cases without resorting to spectral filtering. While critical for many applications in optical quantum information processing, such a source has not previously been demonstrated.
Highlights
Non-classical light has been exploited for a number of purposes, ranging from testing quantum nonlocality [1,2], to various quantum-enhanced technologies including quantum computation [3,4,5], quantum teleportation [6,7], and quantum cryptography [8,9]
We have applied these conditions to type-I degenerate SPDC using a β -barium borate (BBO) crystal, pumped with a beam centered at 405-nm, produced by frequency doubling the beam from an ultrafast titanium-sapphire laser (35-fs pulse duration, 76-MHz repetition rate, and centered at 810-nm)
Relying on a broadband pump and on vector group velocity matching in the SPDC process, we have been able to attain the two important goals of generating: i) pure heralded single photons, and ii) polarization-entangled photon pairs which are unentangled in all other degrees of freedom
Summary
Non-classical light has been exploited for a number of purposes, ranging from testing quantum nonlocality [1,2], to various quantum-enhanced technologies including quantum computation [3,4,5], quantum teleportation [6,7], and quantum cryptography [8,9]. SPDC often results in undesired correlations in frequency-time and transverse momentum-position between the two photons in a given pair [16, 17], which as is well known leads to heralded single photons which are not in a quantum-mechanically pure state [18]. Such heralded single photons, which are described as a statistical mixture of the allowed spectral and spatial modes, cannot interfere with other single photons, and cannot be used as the basis for scalable quantum information processing. In a fifth measurement, we directly verify the presence of polarization entanglement for a two-crystal version of our source
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
