Two-photon interference of the emission from electrically tunable remote quantum dots

Self-assembled quantum dots comprise a versatile system with which to study quantum effects in the solid state. Many devices have been developed that demonstrate controlled charging of a quantum dot(1), Rabi oscillations(2), coherent spin control(3) and electrically injected non-classical photon emission(4). Often referred to as 'artificial atoms', quantum dots have discrete energy levels, making them a viable candidate for encoding qubits. However, unlike single atoms, no two quantum dots are alike. This is a complication for quantum-information applications that require qubits initialized in the same state and interactions between remote systems mediated by indistinguishable photons. We report that truly remote, independent, quantum dots can be tuned to the same energy using large applied electric fields. This allows two-photon interference(5) of their emission under coincidence gating and opens up the possibility of transferring quantum information between remote solid-state sources.