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Physical Review B

Coherent generation of time-bin entangled photon pairs using the biexciton cascade and cavity-assisted piecewise adiabatic passage

Pradyumna K. Pathak, Stephen Hughes

Published Jun 3, 2011• 18 citations
Publisher

Abstract

We present a scheme to realize a deterministic solid-state source of time-bin entangled photon pairs using cavity-assisted piecewise adiabatic passage in a single quantum dot. The quantum dot is embedded inside a semiconductor microcavity, and the interaction of a coherent superposition of two temporally separated input pulses and the cavity mode leads to a piecewise adiabatic passage, which produces a time-bin entangled photon pair through the biexciton-exciton cascade. We show that the entanglement of the generated state can be measured using triple coincidence detection, and we quantify the degree of entanglement through the visibility of the interference. We also discuss the influence of pure dephasing on the entanglement of the generated photon pair. Pronounced interference visibility values of greater than $1/\sqrt{2}$ are predicted in triple coincidence measurement using experimentally achievable parameters, demonstrating that the generated photons could be suitable for applications such as Bell's inequality violation and quantum cryptography.

DOI
10.1103/physrevb.83.245301

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We present a scheme to realize a deterministic solid-state source of time-bin entangled photon pairs using cavity-assisted piecewise adiabatic passage in a single quantum dot. The quantum dot is embedded inside a semiconductor microcavity, and the interaction of a coherent superposition of two temporally separated input pulses and the cavity mode leads to a piecewise adiabatic passage, which produces a time-bin entangled photon pair through the biexciton-exciton cascade. We show that the entanglement of the generated state can be measured using triple coincidence detection, and we quantify the degree of entanglement through the visibility of the interference. We also discuss the influence of pure dephasing on the entanglement of the generated photon pair. Pronounced interference visibility values of greater than 1/21/\sqrt{2}1/2​ are predicted in triple coincidence measurement using experimentally achievable parameters, demonstrating that the generated photons could be suitable for applications such as Bell's inequality violation and quantum cryptography.
We present a scheme to realize a deterministic solid state source of time-bin entangled photon pairs using cavity-assisted stimulated Raman adiabatic passage (STIRAP) in a single quantum dot. The quantum dot is embedded inside a semiconductor cavity, and the interaction of a coherent superposition of two temporally separated input pulses and the cavity mode leads to a two-photon Raman transition, which produces a time-bin entangled photon pair through the biexciton-exciton cascade. We show that the entanglement of the generated state can be measured using triple coincidence detection, and the degree of entanglement is quantified as the visibility of the interference. We also discuss the effect of pure dephasing on entanglement of the generated photon pair. Pronounced interference visibility values of greater than 1/21/\sqrt{2}1/2​ are demonstrated in triple coincidence measurement using experimentally achievable parameters, thus demonstrating that the generated photons are suitable for applications with Bell's inequality violation and quantum cryptography.
We present a scheme for the fast cavity-assisted generation of entangled photon pairs from a single quantum dot coupled to a planar photonic crystal that support two orthogonally polarized cavity modes. We discuss ``within generation'' and ``across generation'' of entangled photons when both the biexciton to exciton, and the exciton to ground-state transitions, are coupled through cavity modes. In the across generation, the photon entanglement is restored through a time delay between the photons. The concurrence, which is a measure of the entanglement between two photons, is greater than 0.7 and 0.8 using experimentally achievable parameters in across generation and within generation, respectively. We also show that the entanglement can be distilled in both cases using a simple spectral filter.
A deterministic "on demand" source of single photons is a basic building block for linear quantum computation \cite{linear}, quantum cryptography \cite{crypto}, quantum teleportation \cite{teleport}, and quantum networks \cite{network}. In all these applications, quantum interference between two single-photon pulses on a symmetric beam splitter has been exploited \cite{review}, which imposes stringent requirement for the implemented single photons to be indistinguishable in all degrees of freedom, including their frequencies, spectral widths, pulse shapes, and polarizations. To generate single photons one requires a pumping mechanism to excite a "two-level emitter" and an efficient channeling of the subsequently emitted photons. The efficiency of the source can be enhanced by coupling the emitter to the waveguide \cite{manga} or a microcavity mode \cite{cklaw}. However, hitherto the solid-state single photon sources realized by using a quantum dot coupled with a microcavity rely on incoherent pumping of excitons, which leads to problems with timing jitter \cite{kiraz}, leading to a trade off between efficiency and indistinguishability. Here we introduce a means to realize a highly efficient solid state source of indistinguishable single photons using cavity-assisted adiabatic Raman passage in a single quantum dot - cavity system. We demonstrate pulse-triggered single photons with 100% efficiency and >90>90>90% indistinguishability using currently available experimental parameters.
We present a formal theory of single quantum dot coupling to a planar photonic crystal that supports quasidegenerate cavity modes and use this theory to describe and optimize entangled-photon pair generation via the biexciton-exciton cascade. In the generated photon pairs, either both photons are spontaneously emitted from the dot or one photon is emitted from the biexciton spontaneously while the other is emitted via the leaky cavity mode. In the strong-coupling regime, the generated photon pairs can be maximally entangled in qualitative agreement with the dressed-state predictions of Johne et al. [Phys. Rev. Lett. 100, 240404 (2008)]. We derive useful analytical formulas for the spectrum of the emitted photon pairs in the presence of exciton and biexciton broadening, which is necessary to connect to realistic experiments and demonstrate the important differences with the approximate dressed-state approach. We also present a method for calculating and optimizing the entanglement between the emitted photons, which can account for postsample spectral filtering. Pronounced entanglement values of greater than 80% are demonstrated using experimentally achievable parameters even without spectral filtering.
We present a scheme for the fast generation of entangled photons from a single quantum dot coupled to a planar photonic crystal that support two orthogonally polarized cavity modes. We discuss ``within generation'' and ``across generation'' of entangled photons when both biexciton to exciton, and exciton to ground state transitions, are coupled through cavity modes. In the across generation, the photon entanglement is restored through a time delay between the photons. The two photon concurrence, which is a measure of entanglement, is greater than 0.7 and 0.8 using experimentally achievable parameters in across generation and within generation, respectively. We also show that the entanglement can be distilled in both cases using a simple spectral filter.
We compute the concurrence of the polarization-entangled photon pairs generated by the biexciton cascade decay of a semiconductor quantum dot. We show how a cavity-induced increase of the photon emission rate reduces the effect of dot dephasing and excitonic fine structure on the concurrence. However, strong dot-cavity couplings, as well as low detection efficiencies, increase the detrimental effect of multiple cascades. This affects the merits of the entangled photon-pair source, beyond what is estimated by quantum tomography.