Time-bin entangled photons from a quantum dot

Abstract

Long distance quantum communication is one of the prime goals in the field of quantum information science. With information encoded in the quantum state of photons, existing telecommunication fibre networks can be effectively used as a transport medium. To achieve this goal, a source of robust entangled single photon pairs is required. Here, we report the realization of a source of time-bin entangled photon pairs utilizing the biexciton-exciton cascade in a III/V self-assembled quantum dot. We analyse the generated photon pairs by an inherently phase-stable interferometry technique, facilitating uninterrupted long integration times. We confirm the entanglement by performing quantum state tomography of the emitted photons, which yields a fidelity of 0.69(3) and a concurrence of 0.41(6) for our realization of time-energy entanglement from a single quantum emitter.

Single pairs of time-bin-entangled photons

“…Recently, generation of entangled photons from a semiconductor quantum dot at a telecom wavelength has been realized [52]. By combination with our technique, and with resonant excitation [25,45] and electrical injection [20], one could make an electrically driven on-demand source of single time-bin-entangled photons at a telecom wavelength. …”

“…In 2005, Simon and Poizat suggested a method [24], but the lack of a suitable metastable state in the quantum dot, essential in their proposal, has prevented implementation. A recent approach by Jayakumar et al [25] is based on a quantum dot, but still allows for a probability of order p 2 to create two photon pairs from the same incoming laser pulse because they split their pulse into two.…”

Tomographic reconstruction of time-bin-entangled qudits

“…QST was previously demonstrated with entangled qudits using OAM modes (up to d = 8) spatial modes (up to d = 3), and time-energy modes (up to d = 4) [16][17][18][19]. To the best of our knowledge, time-bin QST has been previously demonstrated for qubits only [20][21][22][23].…”

Three-dimensional cavity-assisted spontaneous emission as a single-photon source: Two cavity modes and Rabi resonance

“…For scalable and integrable quantum information processing it is furthermore vital to obtain high-efficiency quantum entanglement. Various implementations in recent years include polarization entanglement of photons by means of parametric downconversion in nonlinear optical crystals [2], by using the biexciton (XX) -exciton (X) cascade of single semiconductor QDs [3], or via time-bin entanglement [4]. Beyond that, the usage of the strong coupling of the electromagnetic field with an emitter placed in a high finesse cavity promises the most substantial improvement for both the efficiency of entanglement distribution schemes and demonstration of violation of a Bell inequality at larger scales (see, e.g., Ref.…”