Quantum delocalization in photon-pair generation

Abstract

The generation of correlated photon pairs is a key to the production of entangled quantum states, which have a variety of applications within the area of quantum information. In spontaneous parametric down-conversion-the primary method of generating correlated photon pairs-the associated photon annihilation and creation events are generally thought of as being colocated: The correlated pair of photons is localized with regards to the pump photon and its positional origin. A detailed quantum electrodynamical analysis highlights a mechanism exhibiting the possibility of a delocalized origin for paired output photons: The spatial extent of the region from which the pair is generated can be much larger than previously thought. The theory of both localized and nonlocalized degenerate down-conversion is presented, followed by a quantitative analysis using discrete-volume computational methods. The results may have significant implications for quantum information and imaging applications, and the design of nonlinear optical metamaterials.

Quantum electrodynamics in modern optics and photonics: tutorial

“…Adapted from Ref. [88]. is accordingly governed by the fewer remaining, incoherent rate terms, in this case associated with the much weaker process known as hyper-Rayleigh scattering [82][83][84][85][86][87].…”

Quantum localization issues in nonlinear frequency conversion and harmonic generation

“…[22][23] Here, we focus on another aspect, concerned with the extent of delocalization. In a system of nanoparticles, within each of which there will generally be a system of optical centers able to play the role of one of a coupled pair, it is interesting to observe the effect of increasing particle size.…”

“…23 Within the simplifications outlined earlier, in Section 2, we now consider the possible enhancement to SHG, paying particular heed to the time-reversal symmetry that links SHG to SPDC. As is well known, the fundamental symmetries of significance to optical and electromagnetic phenomena are the parities with respect to charge, space and time inversion -operations denoted by C, P, and T respectively.…”

“…Beyond this specifically local leading term, it emerges that additional contributions can only be of order 3+2p, where p is a positive integer. 23 Therefore, the leading corrections come from fifth order, necessarily requiring that the two additional photon events are the creation and annihilation of a photon in an arbitrary mode -i.e. a virtual photon, fleetingly borrowing energy from the vacuum field.…”

“…In particular, the individual photons that constitute the correlated pairs produced by SPDC can come from separate, distinct locations in the nonlinear crystal, through a delocalized mechanism. [22][23] The work presented within is V 000 0,,n9 o0 concerned with extending the physics behind this new mechanism from a specific optical process (SPDC), and applying it to another optical phenomenon, namely SHG. Identifying the variation of significance in the delocalized mechanism also leads to results that indicate an optimum size for nanoparticles, in a medium designed for frequency conversion.…”