Quantum Interference of Identical Photons from Remote GaAs Quantum Dots

Abstract

Photonic quantum technology provides a viable route to quantum communication 1,2 , quantum simulation 3 , and quantum information processing 4 . Recent progress has seen the realisation of boson sampling using 20 single-photons 3 and quantum key distribution over hundreds of kilometres 2 . Scaling the complexity requires photonic architectures containing a large number of single photons, multiple photon-sources and photon-counters. Semiconductor quantum dots are bright and fast sources of coherent single-photons [5][6][7][8][9] . For applications, a significant roadblock is the poor quantum coherence upon interfering single photons created by independent quantum dots 10,11 . Here, we demonstrate two-photon interference with near-unity visibility using photons from remote quantum dots. Exploiting the quantum interference, we demonstrate a photonic controlled-not circuit and a high-fidelity entanglement between photons of different origins. Our results provide a long-awaited solution to the challenge of creating coherent single-photons in a scalable way. In the near future, they point to a demonstration of quantum advantage using quantum-dot single photons 8 and an implementation of device-independent quantum key distribution 2 .

Violation of Bell's inequality with quantum-dot single-photon sources

“…In such a configuration the two sources and detectors could potentially be integrated on a single chip, which likely would be the most efficient approach. A bottleneck for this implementation would be the need to make two quantum-dot sources indistinguishable, but encouragingly 93% HOM visibility was recently reported between two remote quantum dots [18].…”

Swing-up of quantum emitter population using detuned pulses

“…We now consider the excitation of a specific system, namely a quantum dot excited by an optical laser pulse. Semiconductor quantum dots have already been shown to perform well as deterministic single-photon sources [1,7,9,10,[33][34][35][36], for which a high-fidelity preparation of the excited state is necessary. In such a system, the energy separation of ground and excited state is in the range of 1 − 2 eV and typical detunings of the laser are of the order of several meV.…”

“…Deterministically preparing the excited state of a quantum emitter is a key to many applications in quantum information technology, since the subsequent decay of the excited state yields a single-photon [1][2][3]. Prominent examples for quantum emitters are semiconductor quantum dots [4][5][6][7][8][9][10], strain potentials and defects in monolayers of atomically thin semiconductors [11][12][13], defect centers in diamond [14][15][16][17][18] or in hexagonal boron nitride [19][20][21]. The deterministic preparation relies on the direct excitation of the quantum emitter excited state by an external laser pulse.…”

Limits for quantum networks with semiconductor entangled photon sources

“…The indistinguishabilities are therefore estimated to V 4)%, respectively. The limited coherence is usually attributed to dephasing due to charge and spin noise or phonon scattering [47]. The ratio of the lifetimes of XX and X (i.e.…”