SUPER Scheme in Action: Experimental Demonstration of Red-Detuned Excitation of a Quantum Emitter

Abstract

The quest for the perfect single-photon source includes finding the optimal protocol for exciting the quantum emitter. Coherent optical excitation was, up until now, achieved by tuning the laser pulses to the transition frequency of the emitter, either directly or in average. Recently, it was theoretically discovered that an excitation with two red-detuned pulses is also possible where neither of which would yield a significant upperlevel population individually. We show that the so-called swing-up of quantum emitter population (SUPER) scheme can be implemented experimentally with similar properties to existing schemes by precise amplitude shaping of a broadband pulse. Because of its truly off-resonant nature, this scheme has the prospect of powering high-purity photon sources with superior photon count rate.

Dressed-state analysis of two-color excitation schemes

“…In the proposal [69] as well as in the experimental realisation [72] two Gaussian pulses were used, such that also for the first pulse we now take a Gaussian envelope…”

“…The energy of the biexciton is decreased by the binding energy ∆ B compared to double the exciton energy ω 0 . We set ∆ B = 4 meV, which is typical for quantum dots used in recent experiments [72]. Following the procedure from the two-level system, a transformation to a reference frame rotating with the fre- quency of the first laser leads to…”

“…A radically different approach is the Swing-UP of quantum EmitteR population (SUPER) scheme [69][70][71][72] that exploits the coherence of the quantum system by using off-resonant pulse pairs. The SUPER scheme also circumvents the necessity for polarization filtering, without relying on incoherent or emitter-specific processes like phonon effects in a quantum dot, because the exciting laser frequency is energetically separated from the signal by several millielectronvolts.…”

Phonon-decoupled di-chromatic pumping scheme for highly efficient and indistinguishable single-photon sources

“…Still, exciton preparation is limited to 0.85-0.90 fidelity both in experiments and theory [17,18], thus posing a fundamental limitation towards further increasing the efficiency. Promising strategies involving a periodic swingup scheme [19,20] or stimulated emission from the biexciton level [21][22][23] have been recently proposed. The former resulted in 0.97 population inversion estimated in experiments [20], while the latter has generated single photons with 0.93 indistinguishability and in-fiber efficiency of 0.51 [22].…”

“…Promising strategies involving a periodic swingup scheme [19,20] or stimulated emission from the biexciton level [21][22][23] have been recently proposed. The former resulted in 0.97 population inversion estimated in experiments [20], while the latter has generated single photons with 0.93 indistinguishability and in-fiber efficiency of 0.51 [22]. It is thus natural to ask whether the figures of merit can be further increased towards unity.…”