Near-Transform-Limited Single Photons from an Efficient Solid-State Quantum Emitter

Abstract

By pulsed s-shell resonant excitation of a single quantum dot-micropillar system, we generate long streams of 1000 near-transform-limited single photons with high mutual indistinguishability. The HongOu-Mandel interference of two photons is measured as a function of their emission time separation varying from 13 ns to 14.7 μs, where the visibility slightly drops from 95.9(2)% to a plateau of 92.1(5)% through a slow dephasing process occurring at a time scale of 0.7 μs. A temporal and spectral analysis reveals the pulsed resonance fluorescence single photons are close to the transform limit, which are readily useful for multiphoton entanglement and interferometry experiments. DOI: 10.1103/PhysRevLett.116.213601 Self-assembled InGaAs quantum dots (QDs) are promising single-photon emitters with a high quantum efficiency and a fast decay rate [1]. In the past decades, extensive efforts have been devoted to producing single photons with high purity (that is, a vanishing two-photon emission probability), near-unity indistinguishability, and high extraction efficiency [2][3][4][5][6][7][8][9][10]. These key properties have been compatibly combined simultaneously on the same QD micropillar very recently [11][12][13].An important next challenge is to extend the singlephoton sources to multiple photonic quantum bits [14], as required by various quantum information protocols such as boson sampling [15], quantum teleportation [16], quantum computation [17], and quantum metrology [18]. To this aim, one approach is to use many independent QDs [19] that are tuned into an identical emission wavelength [20] and efficiently emit single photons stringently at the transform limit, that is, T 2 ¼ 2T 1 , where T 2 and T 1 are the photon's coherence time and lifetime, respectively. Another-probably less demanding-solution is based on only one perfect QD emitting single-photon pulse trains with high efficiency [11,12], which are then either demultiplexed into N spatial modes or dynamically controlled using time-bin encoding in a loop-based architecture [21]. Implementing N-photon quantum circuits in this configuration demands streams of N mutually indistinguishable single photons far apart in emission time.However, previous Hong-Ou-Mandel (HOM) type interference experiments [7][8][9][10][11][12][13] were performed with a time separation of only a few nanoseconds between two photons emitted consecutively from a QD. Spectral diffusions [22] with a time scale much slower than nanoseconds were speculated-yet without a conclusive study-to account for the mismatch between the observed near-unity transient indistinguishability and the nonunity time-averaged T 2 =2T 1 ratio [7][8][9][10]13]. Thus, it is highly desirable to study the two-photon interference as a function of their emission time separation and test how far apart the high indistinguishability persists. The ultimate goal is to generate efficient and truly transform-limited single photons, with which perfect interference can be achieved regardless of their time separation, and ...

Phase-tuned entangled state generation between distant spin qubits

“…In order to extend to multiple nodes and realize fault-tolerant operation, we require both distribution rates within the storage time of the entangled state and additional memory qubits. Using current state-ofthe-art light-collection strategies [43,44], the entanglement rate could be improved to 130 kHz. This rate approaches the inverse of electron-spin coherence times in self-assembled QDs [21,23,45], a crucial benchmark for fault tolerant scalability [46].…”

Components of Long-Distance Quantum Communication. Part 2

“…В качестве перспективных квантовых систем, которые можно использовать в интегральных оптических схемах, предлагаются квантовые точки [69,70] и центры окраски в алмазе [71,72] -такие как NV-центры и SiV-центры. Анализируя подход в целом, в качестве основных недостат-ков обычно указывают: низкую эффективность сбора излучения (collection efficiency) точечного источника, в особенности находящегося в материале с высоким показателем преломле-ния; некогерентный характер однофотонных импульсов (отсутствие спектральной ограни-ченности) вследствие большого однородного уширения оптических переходов при комнат-ной температуре; уникальность ка ж дого [73,74], испускание более 1 000 фотонов с неразличимостью (видностью анти-корреляционного провала), превышающей 92% [75], высокая эффективность сбора излуче-ния (более 65%) [73,74,76], генерация перепутан-ных двухфотонных состояний на каскадных переходах [76,77]. В настоящее время активно ведется разработка однофотонных излучателей с электрической накачкой, источников, кото-рые встроены или сильно связаны с интеграль-ными оптическими схемами, а так же исследо-вание новых перспективных систем, таких как дефекты в двумерных материалах и углерод-ные нанотрубки (см.…”

“…Furthermore, it should be also noted that spontaneously emitted single-photon pulses are of exponential fall temporal form with sharp leading edge that complicates synchronization of light pulses when implementing quantum algorithms and reduces efficiency of storage and retrieval of single-photon pulses in quantum memory devices. Today the best parameters of single-photon sources are demonstrated by quantum dots InAs/GaAs at the temperatures of liquid helium: high quality of single-photon states (g 2 ( ) 0 ( ) < 0,01) [73,74], emission of over 1000 photons with indistinguishability (the visibility of the HOM dip) exceeding 92% [75], high collection efficiency (over 65%) [73,74,76], generation of entangled two-photon states via cascade transitions [76,77]. Currently, the topics of active research are electrically pumped single-photon sources, sources that are built-in or tightly connected with photonic chips, and new promising systems, such as defects in two-dimensional materials and carbon nano-tubes (see the recent review [78]).…”

A tunable waveguide-coupled cavity design for scalable interfaces to solid-state quantum emitters

“…Cavity enhancement of quantum dots in III-V materials has enabled strong light-matter coupling 1 and record rates of indistinguishable photons. [2][3][4][5] Recent advances in diamond nanofabrication 6 have enabled the fabrication of free-standing photonic crystal cavities in diamond for the enhancement of the zero phonon line (ZPL) transition of silicon vacancy centers 7,8 and negatively charged nitrogen vacancy (NV) centers. [9][10][11][12][13][14][15][16][17][18][19] However, there are currently two main challenges limiting progress in scaling to multiple coupled emitter-cavity systems for distributed quantum networks.…”