[Paper Review] Indistinguishable photons from independent semiconductor single-photon devices

Kaoru Sanaka, Alexander Pawlis+3 more|ArXiv.org|Mar 10, 2009

Quantum Information and Cryptography3 citations

TL;DR

This paper demonstrates experimentally indistinguishable photons from two independent semiconductor single-photon sources based on fluorine donors in ZnSe/ZnMgSe quantum wells. Using a Hong-Ou-Mandel interference setup, the authors achieve a measured indistinguishability of 65±13% and a two-photon correlation time of 74±38 ps, indicating near-lifetime-limited emission and potential for scalable photonic quantum technologies.

ABSTRACT

We demonstrate quantum interference between photons generated by the radiative decay processes of excitons that are bound to isolated fluorine donor impurities in ZnSe/ZnMgSe quantum-well nanostructures. The ability to generate single photons from these devices is confirmed by auto-correlation experiments, and indistinguishability of single photons from two independent devices is confirmed via a Hong-Ou-Mandel dip. These results indicate that donor impurities in appropriately engineered semiconductor structures can portray atom-like homogeneity and coherence properties, potentially enabling scalable technologies for future large-scale optical quantum computers and quantum communication networks.

Motivation & Objective

• To achieve quantum interference between photons from independent semiconductor single-photon sources for scalable quantum information processing.
• To address the challenge of spectral and temporal inhomogeneity in conventional quantum dot sources by using isolated donor impurities in ZnSe.
• To demonstrate that donor-bound excitons in engineered semiconductor nanostructures can exhibit atom-like coherence and indistinguishability.
• To enable scalable, chip-integrated photonic quantum technologies by providing a source of highly indistinguishable single photons.
• To explore the feasibility of using these sources as optical qubits or for quantum memory in long-distance quantum communication networks.

Proposed method

• Utilized neutral fluorine donors in ZnSe/ZnMgSe quantum-well nanostructures as single-photon emitters via radiative recombination of donor-bound excitons (D₀X).
• Employed pulsed above-bandgap excitation (410 nm) to trigger photon emission and measured emission spectra to confirm single-photon operation via auto-correlation histograms.
• Performed a Hong-Ou-Mandel (HOM) interference experiment by combining photons from two independent devices on a beam splitter to measure indistinguishability.
• Modelled the two-photon wavefunction using time-dependent amplitude functions α(t) and β(t), with interference visibility governed by the overlap integral in Eq. (2).
• Fitted the HOM dip data to extract indistinguishability I and correlation time τc, accounting for background counts gback and dephasing effects.
• Used streak camera measurements to estimate timing jitter (40 ps) and validate the temporal broadening of photon wavepackets.

Experimental results

Research questions

• RQ1 Can photons from two independent semiconductor single-photon sources exhibit quantum interference, indicating indistinguishability?
• RQ2 To what extent do donor-bound excitons in ZnSe nanostructures produce spectrally and temporally homogeneous single photons?
• RQ3 What limits the indistinguishability of photons from independent sources in this system?
• RQ4 Can the observed indistinguishability be improved through device engineering such as microcavities or enhanced spatial filtering?
• RQ5 Can this system serve as a scalable, on-chip source of indistinguishable photons for linear optical quantum computing?

Key findings

• The experiment achieved a measured two-photon interference visibility of 31% in the Hong-Ou-Mandel dip, confirming quantum interference between photons from independent sources.
• The deduced photon indistinguishability was 65±13%, indicating high coherence and potential for near-unity indistinguishability with further optimization.
• The two-photon correlation time was measured as 74±38 ps, which is comparable to the spontaneous emission lifetime, suggesting near-lifetime-limited emission.
• Background coincidence counts (gback ≈ 0.51±0.06) were higher than expected due to lack of spatial filtering in the two-source experiment, increasing stray photon contributions.
• The primary reduction in indistinguishability is attributed to imperfect spatial mode overlap, with timing jitter and residual spectral inhomogeneity contributing less significantly.
• The results indicate that donor-impurity-based emitters in ZnSe offer a promising path toward scalable, solid-state sources of indistinguishable photons for quantum technologies.