Interference with a quantum dot single-photon source and a laser at telecom wavelength

Abstract

The interference of photons emitted by dissimilar sources is an essential requirement for a wide range of photonic quantum information applications. Many of these applications are in quantum communications and need to operate at standard telecommunication wavelengths to minimize the impact of photon losses and be compatible with existing infrastructure. Here we demonstrate for the first time the quantum interference of telecom-wavelength photons from an InAs/GaAs quantum dot single-photon source and a laser; an important step towards such applications. The results are in good agreement with a theoretical model, indicating a high degree of indistinguishability for the interfering photons.Single-photon sources are essential components for many photonic quantum information technologies, ranging from linear-optics quantum computation [1] to teleportation of quantum bits [2] and large scale quantum networks.[3] The interference of two independently generated photon states on a beam splitter is an important physical mechanism required for the realization of most of these schemes.Apart from the common implementation with two identical single photons, [4] Of even greater immediate importance are applications related to quantum communication and quantum key distribution [8,9] (QKD), the most developed technology based on photonic quantum bits. The most widely implemented scheme for QKD makes use of weak coherent laser pulses.[10] Interference of these states with single photons from an entangled pair to perform a Bell-state measurement thereby enables quantum teleportation. This * jan.huwer@crl.toshiba.co.uk opens up the route to develop a so-called quantum relay [11] or all-photonic quantum repeater, [12] indispensable to reduce noise and extend the transmission distances in future networks that are strongly limited by photon losses in optical fiber. More generally, recent theoretical studies [13] have shown that, for limited experimental resources, a hybrid approach for the teleportation of continuous variable systems by using discrete single-photon entangled states is expected to have significant advantages over its continuous-variable counterpart. The interference between dissimilar photon sources is thereby of great interest both for fundamental science and a large number of technological applications.Most experiments demonstrated so far have been performed with heralded single photon sources based on non-linear optical processes. [5,6,14] These sources obey Poissonian statistics, intrinsically deteriorating the single-photon character and making them non-desirable for certain applications. More recently, quantum dots (QDs) based on III-V semiconductor compounds have proven to be one of the most promising sub-Poissonian sources, generating deterministic single photons as well as entangled photon pairs. [15][16][17][18] In the past, these systems have been successfully used to demonstrate interference of single photons with emission from a laser [19] and subsequently the teleportation of laser-generated qubits.[20] ...

Two-photon interference in the telecom C-band after frequency conversion of photons from remote quantum emitters

“…mid-and long-distance quantum networks) [28]. In the telecom C-band, current state-ofthe-art showed TPI with one down-converted quantum emitter and a laser [29,30]. As a clear step forward, we here demonstrate TPI with on-demand generated photons of two distinct remote quantum dots.…”

Quantum-Dot-Based Telecommunication-Wavelength Quantum Relay

“…The situation is rather different when approaching superposition states with θ ¼ π=2. Here, two-photon interference comes into play which is dominated by the Poissonian statistics of the input qubits [20,26,36] and not the relay itself, lowering the teleportation fidelities. Still, minimum values are safely above the classical limit of 2=3, indicating possible quantum teleportation for arbitrary input states.…”

“…[25,26] but with an improved ultralow QD density (< 0.02 μm −2 ). The device is operated at 10 K and is optically excited with continuous-wave 1064-nm laser light at a bias of 0 V. The excitation power is set for equal intensity of the biexciton (2X) and exciton (X) spectral lines, measured with an InGaAs array in a grating spectrometer.…”

“…Nevertheless, the experiment made use of a conventional QD emitting at short wavelength, suffering from high losses when being transmitted over a long optical fiber and, therefore, not suitable for a scalable architecture. Great effort has been put into the development of QDs emitting at telecommunication wavelengths [21][22][23][24], culminating in independent demonstrations of entangled photon emission [25] and interference with laser photons [26]. Here, we report the implementation of a quantum-relay experiment in the telecommunication O band (close to 1310 nm), suitable for secure quantumcommunication applications and, at the same time, fully compatible with the existing communication infrastructure regarding networks and sources.…”

Magneto-optical spectroscopy of single charge-tunable InAs/GaAs quantum dots emitting at telecom wavelengths

“…Advances in the development of superconducting detectors operating at cryogenic temperatures [6] allow detection efficiencies exceeding 90% [7], making single-photon experiments and technologies eminently feasible. The growing interest in the field of long wavelength quantum dots is demonstrated by recent achievements such as the demonstration of bright sources of indistinguishable photons [8], interference of photons emitted by dissimilar sources [9], entangled photon pair generation [10] and exciton fine-structure splitting manipulation [11] in the telecom wavelength band.…”