Microscopic theory of cavity-enhanced single-photon emission from optical two-photon Raman processes

Abstract

We consider cavity-enhanced single-photon generation from stimulated two-photon Raman processes in three-level systems. We compare four fundamental system configurations, one Λ-, one Vand two ladder (Ξ-) configurations. These can be realized as subsystems of a single quantum dot or of quantum-dot molecules. For a new microscopic understanding of the Raman process, we analyze the Heisenberg equation of motion applying the cluster-expansion scheme. Within this formalism an exact and rigorous definition of a cavity-enhanced Raman photon via its corresponding Raman correlation is possible. This definition for example enables us to systematically investigate the ondemand potential of Raman-transition-based single-photon sources. The four system arrangements can be divided into two subclasses, Λ-type and V-type, which exhibit strongly different Ramanemission characteristics and Raman-emission probabilities. Moreover, our approach reveals whether the Raman path generates a single photon or just induces destructive quantum interference with other excitation paths. Based on our findings and as a first application, we gain a more detailed understanding of experimental data from the literature. Our analysis and results are also transferable to the case of atomic three-level-resonator systems, and can be extended to more complicated multi-level schemes.This approach leads to new microscopic insight into the Raman process which, in general, cannot be extracted directly from the observation of optical spectra. As an example, Fig. 2 shows the time development of the cavity-arXiv:1711.11490v2 [cond-mat.mes-hall]

Pulse shaping for on-demand emission of single Raman photons from a quantum-dot biexciton

“…For the single photon emission of interest in the present work we have previously shown that the Raman resonance condition non-trivially depends on the shape of the control pulse triggering the emission [15,20]. Moreover, the Raman process can also act as a source of excitation-induced quantum interference instead of as a source of single-photon emission [20]. Both these aspects play an increasingly important role for elevated control pulse intensities and generally tend to undermine our quest for entering the on-demand regime for single Raman photon generation.…”

“…To unlock the full potential of quantum applications high single-photon emission probabilities are required, exceeding 66% for linear quantum computing [21] and 50% for Boson sampling [22]. For the single photon emission of interest in the present work we have previously shown that the Raman resonance condition non-trivially depends on the shape of the control pulse triggering the emission [15,20]. Moreover, the Raman process can also act as a source of excitation-induced quantum interference instead of as a source of single-photon emission [20].…”

“…Exactly on resonance, however, at ∆ BX/XG C = 0, where one would expect the total cavity emission probability to peak (not shown in Fig. 2), the Raman emission rate is close to zero due to quantum interference of different emission channels [20]. As a consequence we find the resonance from nearby real transitions to be strongest if the cavity is positioned between the electronic quantum dot resonances, with a slight asymmetry favoring the exciton to ground state transition.…”

“…with destructive quantum interference [20], is marginal at high pulse energies, so that the quantum light source can be characterized as an on-demand source with emission probabilities of ∼ 80 %. At higher temperatures of T = 10 K, the optimized emission probability still exceeds on-demand limit for ∆ BX C = +0.3 meV.…”

“…This single-photon emission can be enhanced using an optical cavity. Related types of optical Raman processes which allow at least partial optical control of the properties of the emitted photon, such as polarization state and frequency, were previously studied in detail in different three-level systems [14,[16][17][18][19][20].…”