Interference of Single Photons from Two Separate Semiconductor Quantum Dots

We demonstrate and characterize interference between discrete photons emitted by two separate semiconductor quantum dot states in different samples excited by a pulsed laser. Their energies are tuned into resonance using strain. The photons have a total coalescence probability of 18.1% and the coincidence rate is below the classical limit. Postselection of coincidences within a narrow time window increases the coalescence probability to 47%. The probabilities are reduced from unity because of dephasing and the postselection value is also reduced by the detector time response.

Figure 1

(a) Schematic of QD samples and interferometer. (b) Area-normalized emission lines for QD1 (○) and QD2 (▴). (c) Time-dependent fluorescence from QD1. (d) Time-dependent fluorescence from QD2.

Figure 2

(a) Autocorrelation for QD1; residual counts in the center peak are 9% of those in the other peaks. (b) Autocorrelation for QD2; residual counts in the center peak are 7%.

Figure 3

(a) Correlation of the interference for orthogonal polarizations with simulated curve. (b) Correlation of the interference for parallel polarizations with simulated curve. (c) Close-up of $\tau =0$ peak for orthogonal (△) and parallel (●) polarizations. The solid and dashed curves are simulations including the detectors’ time response, while the dash-dotted curve is the expected curve for infinitely fast detectors.