Entanglement, coherence, and redistribution of quantum resources in double spontaneous down-conversion processes

Abstract

We study the properties of bisqueezed tripartite Gaussian states created by two spontaneous parametric down-conversion processes that share a common idler. We give a complete description of the quantum correlations across all partitions, as well as of the genuine multipartite entanglement, obtaining analytical expressions for most of the quantities of interest. We find that the state contains genuine tripartite entanglement, in addition to the bipartite entanglement among the modes that are directly squeezed. We also investigate the effect of homodyne detection of the photons in the common idler mode, and analyze the final reduced state of the remaining two signal modes. We find that this measurement leads to a conversion of the coherence of the two signal modes into entanglement, a phenomenon that can be regarded as a redistribution of quantum resources between the modes. The applications of these results to quantum optics and circuit quantum electrodynamics platforms are also discussed.

Coherence, Interference and Visibility

“…For example, recently it has been shown that in double parametric pumping of a superconducting microwave cavity, coherence between photons in separate frequency modes can arise because of the absence of which-way information in the frequency space [35]. Similarly, in a double spontaneous down-conversion processes, it has been shown that coherence in photons in the signal is induced due to lack of which-path information for the photons emitted in the idler [36]. Coherence has also found applications in quantum metrology [37].…”

Generating Multimode Entangled Microwaves with a Superconducting Parametric Cavity

“…The pump at f p1 produces TMS between f 1 and f 2 , while the pump at f p2 coherently couples f 3 with f 1 . In the BS scheme [35], the pump tones are applied at f p1 = f 1 + f 2 and f p2 = f 2 + f 3 , directly producing TMS correlations between the pairs. See Table I for the exact frequencies used.…”

Listening to the quantum vacuum: a perspective on the dynamical Casimir effect

“…The entangled microwave photons could also be used as a source for a quantum radar. Photons can be generated from vacuum by using not only one, but several pumps [11], aiming at using multimode correlations as a resource [12]. And there is more to it.…”