Multiphoton interference is at the heart of photonic quantum technologies. Arrays of integrated cavities can support bright sources of single photons with high purity and small footprint, but the inevitable spectral distinguishability between photons generated from nonidentical cavities is an obstacle to scaling. In principle, this problem can be alleviated by measuring photons with high timing resolution, which erases spectral information through the time-energy uncertainty relation. Here, we experimentally demonstrate that detection can be implemented with a temporal resolution sufficient to interfere photons detuned on the scales necessary for cavity-based integrated photon sources. By increasing the effective timing resolution of the system from 200 to 20 ps, we observe a 20% increase in the visibility of quantum interference between independent photons from integrated microring resonator sources that are detuned by 6.8 GHz. We go on to show how time-resolved detection of nonideal photons can be used to improve the fidelity of an entangling operation and to mitigate the reduction of computational complexity in boson sampling experiments. These results pave the way for photonic quantum information processing with many photon sources without the need for active alignment.
Multiphoton interference is at the heart of photonic quantum technologies. Arrays of integrated cavities can support bright sources of single photons with high purity and small footprint, but the inevitable spectral distinguishability between photons generated from nonidentical cavities is an obstacle to scaling. In principle, this problem can be alleviated by measuring photons with high timing resolution, which erases spectral information through the time-energy uncertainty relation. Here, we experimentally demonstrate that detection can be implemented with a temporal resolution sufficient to interfere photons detuned on the scales necessary for cavity-based integrated photon sources. By increasing the effective timing resolution of the system from 200 to 20 ps, we observe a 20% increase in the visibility of quantum interference between independent photons from integrated microring resonator sources that are detuned by 6.8 GHz. We go on to show how time-resolved detection of nonideal photons can be used to improve the fidelity of an entangling operation and to mitigate the reduction of computational complexity in boson sampling experiments. These results pave the way for photonic quantum information processing with many photon sources without the need for active alignment.
An integrated source of time-energy entangled photons is demonstrated through resonantly enhanced spontaneous four-wave mixing in a silicon micro-ring resonator. A Franson type set-up is employed to show the quantum interference between photon pairs with a visibility exceeding 90% and a violation of the Bell's inequality by more than 10 standard deviations. The high spectral brightness and the extremely small footprint of our source make it suitable for the development of quantum information protocols integrated on chip.
Abstract Integrated photonics represents a technology that could greatly improve quantum communication networks in terms of cost, size, scaling, and robustness. A key benchmark for this is to demonstrate their performance in complex quantum networking protocols, such as entanglement swapping between truly independent photon-pair sources. Here, using two independent, asynchronously-pumped, integrated Si 3 N 4 microring resonator photon-pair sources, operating in the continuous-wave regime with time-resolved detections, we obtained state of the art Hong–Ou–Mandel (93.2 ± 1.6%) and entanglement swapping (91.2 ± 3.4%) visibilities, while maintaining high rates. The time-resolved detection facilitates high spectral purities without the need for spectral filtering. Our results demonstrate the potential of such telecom-band sources for practical, real-world quantum communication.
Quantum interference between identical photons lies at the heart of our plan to construct a silicon photonic quantum computer. Several ground-breaking experiments have demonstrated the on-chip interference between photons generated in spiral [1] and ring resonator [2] sources. However, these two-photon experiments have relied on detecting the simultaneous arrival of a pair of photons from either source. In order that such experiments can be scaled-up, we require the multiplexing of probabilistic photon pair sources into an on-demand single photon source [3]. A first step towards this is to demonstrate heralded single photons from different sources will retain the purity and indistinguishability required to interfere with high visibility [4]. In our work we examine photon pair production by spontaneous four-wave mixing in a silicon waveguide source and determine the factors that limit the heralded two-photon interference visibility. We present a novel approach to modelling this generation process using the joint- temporal amplitude and compare our results with experimental data. [1] On-chip quantum interference between silicon photon-pair sources, Nature Photonics 8, 104, (2014). [2] Qubit entanglement between ring-resonator photon-pair sources on a silicon chip, Nature Communications 6, 7948, (2015). [3] Active temporal and spatial multiplexing of photons, Optica 3, 127, (2016) [4] Indistinguishable photon pair generation using two independent silicon wire waveguides, New Journal of Physics 13, 065005, (2011).
Abstract Entanglement is a counterintuitive feature of quantum physics that is at the heart of quantum technology. High-dimensional quantum states offer unique advantages in various quantum information tasks. Integrated photonic chips have recently emerged as a leading platform for the generation, manipulation and detection of entangled photons. Here, we report a silicon photonic chip that uses interferometric resonance-enhanced photon-pair sources, spectral demultiplexers and high-dimensional reconfigurable circuitries to generate, manipulate and analyse path-entangled three-dimensional qutrit states. By minimizing on-chip electrical and thermal cross-talk, we obtain high-quality quantum interference with visibilities above 96.5% and a maximally entangled-qutrit state with a fidelity of 95.5%. We further explore the fundamental properties of entangled qutrits to test quantum nonlocality and contextuality, and to implement quantum simulations of graphs and high-precision optical phase measurements. Our work paves the path for the development of multiphoton high-dimensional quantum technologies.
Interference of multiple photons via a linear-optical network has profound applications for quantum foundation, quantum metrology, and quantum computation. Particularly, a boson sampling experiment with a moderate number of photons becomes intractable even for the most powerful classical computers. Scaling up from small-scale experiments requires highly indistinguishable single photons, which may be prohibited for many physical systems. Here we report a time-resolved multiphoton interference experiment by using photons not overlapping in their frequency spectra from three atomic-ensemble quantum memories. Time-resolved measurement enables us to observe nonclassical multiphoton correlation landscapes, which agree well with theoretical calculations. Symmetries in the landscapes are identified to reflect symmetries of the optical network. Our experiment can be further extended to realize boson sampling with many photons and plenty of modes, which thus may provide a route towards quantum supremacy with nonidentical photons.
Interactions between solid-state quantum emitters and cavities are important for a broad range of applications in quantum communication, linear optical quantum computing, nonlinear photonics, and photonic quantum simulation. These applications often require combining many devices on a single chip with identical emission wavelengths in order to generate two-photon interference, the primary mechanism for achieving effective photon-photon interactions. Such integration remains extremely challenging due to inhomogeneous broadening and fabrication errors that randomize the resonant frequencies of both the emitters and cavities. In this Letter, we demonstrate two-photon interference from independent cavity-coupled emitters on the same chip, providing a potential solution to this long-standing problem. We overcome spectral mismatch between different cavities due to fabrication errors by depositing and locally evaporating a thin layer of condensed nitrogen. We integrate optical heaters to tune individual dots within each cavity to the same resonance with better than 3 μeV of precision. Combining these tuning methods, we demonstrate two-photon interference between two devices spaced by less than 15 μm on the same chip with a postselected visibility of 33%, which is limited by timing resolution of the detectors and background. These results pave the way to integrate multiple quantum light sources on the same chip to develop quantum photonic devices.