Quantum Interference of Single Photons from Remote Nitrogen-Vacancy Centers in Diamond

Abstract

We demonstrate quantum interference between indistinguishable photons emitted by two nitrogenvacancy (NV) centers in distinct diamond samples separated by two meters. Macroscopic solid immersion lenses are used to enhance photon collection efficiency. Quantum interference is verified by measuring a value of the second-order cross-correlation function g (2) (0) = 0.35 ± 0.04 < 0.5. In addition, optical transition frequencies of two separated NV centers are tuned into resonance with each other by applying external electric fields. Extension of the present approach to generate entanglement of remote solid-state qubits is discussed.The interference of two identical photons impinging on a beamsplitter leads to perfect coalescence where both photons leave through the same output port. This fundamental effect, known as Hong-Ou-Mandel (HOM) interference [1], is a consequence of bosonic statistics for indistinguishable particles. HOM interference has been demonstrated using single photon pairs from parametric down-conversion [2] and delayed photons from a single photon source [3][4][5]. HOM interference has recently drawn attention as a resource for entanglement generation between distinct single-photon emitters with many potential applications in quantum information science [6]. The effect has been observed for photons emitted by pairs of atoms [7] and trapped ions [8], and has been used for entanglement generation of remote trapped ions [9]. While isolated atoms and ions, which are nominally identical, are a natural source of indistinguishable photons, extending these ideas to condensed matter systems can be challenging since two solid-state emitters are generally distinguishable because of their different local environments. This Letter demonstrates quantum interference of two photons produced by nitrogen-vacancy (NV) impurities in distinct diamond samples separated by two meters. Complementing the recent work involving other solid-state systems [10][11][12][13], the present solid-state realization is particularly significant, since electronic and nuclear spins associated with NV centers can be used as a robust solid-state qubit memory, yielding potential scalable architectures for quantum networks [14,15]. Specifically, in combination with a recent demonstration of spinphoton entanglement [16], the present work paves the way for entanglement generation between remote solidstate qubits.Unlike those associated with atoms in free space, the optical properties of NV centers embedded in a solid state vary substantially from emitter to emitter, especially in distinct samples. This inhomogeneity is due to variation in the local environments of NV centers and, in particular, to variation in the local strain. Furthermore, coincidence experiments are limited by the collection efficiency for light emitted by the NV center. While a wide variety of approaches are currently being explored to enhance the collection efficiency [17][18][19][20], we here utilize solid immersion lenses (SILs) fabricated from bulk diamond [21] to facili...

Nonlinear optical signals and spectroscopy with quantum light

“…Eqs. (283) - (285) are simulated below using the typical parameters of the two photon interference experiments (Ates et al, 2012;Bernien et al, 2012;Coolen et al, 2008;Lettow et al, 2010;Patel et al, 2010;Sanaka et al, 2012;Santori et al, 2002;Sipahigil et al, 2012;Trebbia et al, 2010;Wolters et al, 2013). Photon indistinguishability depends on the molecular transition frequencies.…”

Heralded entanglement between solid-state qubits separated by three metres

“…Solids are an attractive platform for such registers, as the use of nanofabrication and material design may enable well-controlled and scalable qubit systems [14]. The potential impact of quantum networks on science and technology has recently spurred research efforts towards generating entangled states of distant solid-state qubits [15][16][17][18][19][20][21].…”

“…Solids are an attractive platform for such registers, as the use of nanofabrication and material design may enable well-controlled and scalable qubit systems [14]. The potential impact of quantum networks on science and technology has recently spurred research efforts towards generating entangled states of distant solid-state qubits [15][16][17][18][19][20][21].A prime candidate for a solid-state quantum register is the nitrogen-vacancy (NV) defect centre in diamond. The NV centre combines a long-lived electronic spin (S=1) with a robust optical interface, enabling measurement and high-fidelity control of the spin qubit [15,[22][23][24].…”

Efficient Teleportation Between Remote Single-Atom Quantum Memories

“…The demonstrated ability to teleport a quantum state between nonidentical memories opens up new perspectives for solid-state-based approaches to quantum networks, where identical network nodes are hard to realize [24][25][26][27]. Moreover, with the use of optical cavities we have put teleportation between material systems into a regime where the time needed for a successful teleportation event (about 0.1 s at a repetition rate of 10 kHz) is shorter than the coherence times observed in single atoms [28].…”