- 标题
- 摘要
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- 实验方案
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[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Interaction between Microwave and Mesoscopic Circuits in Cavity-circuit Quantum Electrodynamics
摘要： Mesoscopic electric circuits can exhibit a large number of effects relevant to quantum mechanics, quantum electrodynamics and quantum statistics. The topic presented here can be identified as an analog of conventional cavity quantum electrodynamics, where the quantum objects are multilevel atoms and quantized optical fields (photons), namely, a theoretical subject called “cavity-circuit quantum electrodynamics”, where the atoms are replaced with quantum mesoscopic circuits, will be developed. We will study the quantum characteristics of the interaction between the quantum mesoscopic circuits and the quantized electromagnetic field at microwave frequencies. These issues include quantum entangled eigenstates of two coupled mesoscopic circuits, time evolution of the circuit energy quanta (governed by the time-dependent Schr?dinger equation) and entanglement transfer between external photons and mesoscopic circuit energy quanta. Since there is inevitable electromagnetic interaction such as mutual capacitance and inductance coupling between two neighboring circuits, the quantum effects resulting from the aforementioned quantized circuit coupling would unavoidably affect the relevant processes in quantum computing devices and hence they deserve consideration in some issues of quantum information.
关键词： Quantum computing,Microwave photons,Quantum entanglement,Mesoscopic circuits,Quantum electrodynamics
更新于2025-09-19 17:13:59
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An efficient entangled-photon source from semiconductor quantum dots
摘要： Photon entanglement, also known as “Spooky Action at a Distance”, is a promising solution to quantum cryptography and quantum computing. The former will construct a cryptosystem that is impossible to break, and the latter will be capable of solving specific problems much more quickly than any classical computer. An ideal entangled-photon source meeting the following criteria is needed for eventually the practical implementation of quantum information processing: on-demand generation, high-fidelity, ultrabright, high extraction efficiency, and high-temperature operation. For practical applications, it is preferred to have a simple approach that is compatible with current solid-state technologies. Self-organized semiconductor quantum dots (QDs) represent a promising option as an on-demand source of a triggered single-photon and entangled-photon pairs, through the radiative recombination of excitons and biexcitons.
关键词： quantum computing,semiconductor quantum dots,entangled-photon source,quantum cryptography
更新于2025-09-19 17:13:59
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Fast Gate-Based Readout of Silicon Quantum Dots Using Josephson Parametric Amplification
摘要： Spins in silicon quantum devices are promising candidates for large-scale quantum computing. Gate-based sensing of spin qubits offers a compact and scalable readout with high fidelity, however, further improvements in sensitivity are required to meet the fidelity thresholds and measurement timescales needed for the implementation of fast feedback in error correction protocols. Here, we combine radio-frequency gate-based sensing at 622 MHz with a Josephson parametric amplifier, that operates in the 500–800 MHz band, to reduce the integration time required to read the state of a silicon double quantum dot formed in a nanowire transistor. Based on our achieved signal-to-noise ratio, we estimate that singlet-triplet single-shot readout with an average fidelity of 99.7% could be performed in 1 μs, well below the requirements for fault-tolerant readout and 30 times faster than without the Josephson parametric amplifier. Additionally, the Josephson parametric amplifier allows operation at a lower radio-frequency power while maintaining identical signal-to-noise ratio. We determine a noise temperature of 200 mK with a contribution from the Josephson parametric amplifier (25%), cryogenic amplifier (25%) and the resonator (50%), showing routes to further increase the readout speed.
关键词： quantum computing,spin qubits,gate-based sensing,silicon quantum dots,Josephson parametric amplification
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Splicing ET (error-tolerant) Quantum Computing System
摘要： In this paper, we develop a system with redundant splicing topology by studying the ET (error-tolerant) unique advantages in topology. And tapped the potential of quantum computing. Through theoretical analysis and modeling, it reveals various possibilities for the design of two-dimensional and even three-dimensional quantum computing systems, which are widely neglected in the field of quantum computing, and combines some features of previous ET system design. And design methodology is discussed; the network design of the novel quantum computing system can be further introduced into the unique topology.
关键词： splicing,quantum computing system,error-tolerant
更新于2025-09-16 10:30:52
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A silicon quantum-dot-coupled nuclear spin qubit
摘要： Single nuclear spins in the solid state are a potential future platform for quantum computing, because they possess long coherence times and offer excellent controllability. Measurements can be performed via localized electrons, such as those in single atom dopants or crystal defects. However, establishing long-range interactions between multiple dopants or defects is challenging. Conversely, in lithographically defined quantum dots, tunable interdot electron tunnelling allows direct coupling of electron spin-based qubits in neighbouring dots. Moreover, the compatibility with semiconductor fabrication techniques may allow for scaling to large numbers of qubits in the future. Unfortunately, hyperfine interactions are typically too weak to address single nuclei. Here we show that for electrons in silicon metal–oxide–semiconductor quantum dots the hyperfine interaction is sufficient to initialize, read out and control single 29Si nuclear spins. This approach combines the long coherence times of nuclear spins with the flexibility and scalability of quantum dot systems. We demonstrate high-fidelity projective readout and control of the nuclear spin qubit, as well as entanglement between the nuclear and electron spins. Crucially, we find that both the nuclear spin and electron spin retain their coherence while moving the electron between quantum dots. Hence we envision long-range nuclear–nuclear entanglement via electron shuttling. Our results establish nuclear spins in quantum dots as a powerful new resource for quantum processing.
关键词： entanglement,hyperfine interaction,nuclear spins,quantum dots,silicon,coherence times,quantum computing
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Tailoring Single-Frequency VECSELs for Quantum Technology Applications
摘要： Many quantum technology applications, such as quantum information processing, precision metrology, and atomic clocks, rely on lasers at many different wavelengths with demanding characteristics in terms of power, linewidth, beam quality, and intensity noise. These lasers are typically used to detect or change the quantum states of neutral atoms and ions. Besides the need for precisely defined features fitting a specific atom/ion system, there is an increasing need to make such lasers more affordable, as well as easier to use and tailor, in order to ensure faster transit from lab to real applications. Vertical-External-Cavity Surface-Emitting Lasers (VECSELs, aka. OPSLs or SDLs) are optically pumped semiconductor lasers that combine the benefits of semiconductor quantum well -lasers; the wavelength versatility and the wide pump absorption bandwidth, with the benefits of diode-pumped solid-state lasers; the high output power and excellent beam quality. The external cavity geometry of VECSELs enables the insertion of intracavity wavelength selective elements for tunable single-frequency operation, and the insertion of nonlinear crystals for efficient intracavity frequency conversion. These features make VECSELs very promising candidates to address the needs of quantum technology and other high impact applications. We present compact turnkey single-frequency VECSELs tailored for quantum technology applications, for generation and manipulation of trapped ions for quantum computing. Our previous demonstration was focused on VECSEL-based systems at 279.6 nm for Doppler cooling and at 285.3 nm for photoionization of magnesium ions. Here, we focus on wavelength extension and tailoring the single-frequency operation for use with several other promising ions, such as beryllium at 313 nm and 235 nm. We present very recent results of Watt-level single-frequency emission at challenging 1252 nm and 940 nm wavelengths, which are prerequisites for high power emission at 313 nm and 235 nm, as well as recent developments on the laser platform. We believe that VECSELs can potentially replace many of the laser systems currently in use and enable new quantum technology applications.
关键词： single-frequency lasers,VECSELs,quantum computing,quantum technology,trapped ions
更新于2025-09-12 10:27:22
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Physical-Layer Supervised Learning Assisted by an Entangled Sensor Network
摘要： Many existing quantum supervised learning (SL) schemes consider data given a priori in a classical description. With only noisy intermediate-scale quantum (NISQ) devices available in the near future, their quantum speedup awaits the development of quantum random access memories (qRAMs) and fault-tolerant quantum computing. However, there also exist a multitude of SL tasks whose data are acquired by sensors, e.g., pattern classification based on data produced by imaging sensors. Solving such SL tasks naturally requires an integrated approach harnessing tools from both quantum sensing and quantum computing. We introduce supervised learning assisted by an entangled sensor network (SLAEN) as a means to carry out SL tasks at the physical layer. The entanglement shared by the sensors in SLAEN boosts the performance of extracting global features of the object under investigation. We leverage SLAEN to construct an entanglement-assisted support-vector machine for data classification and entanglement-assisted principal component analyzer for data compression. In both schemes, variational circuits are employed to seek the optimum entangled probe states and measurement settings to maximize the entanglement-enabled enhancement. We observe that SLAEN enjoys an appreciable entanglement-enabled performance gain, even in the presence of loss, over conventional strategies in which classical data are acquired by separable sensors and subsequently processed by classical SL algorithms. SLAEN is realizable with available technology, opening a viable route toward building NISQ devices that offer unmatched performance beyond what the optimum classical device is able to afford.
关键词： Quantum supervised learning,Support-vector machine,Entangled sensor network,Principal component analyzer,Quantum computing,Quantum sensing
更新于2025-09-11 14:15:04
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Computer-automated tuning procedures for semiconductor quantum dot arrays
摘要： As with any quantum computing platform, semiconductor quantum dot devices require sophisticated hardware and controls for operation. The increasing complexity of quantum dot devices necessitates the advancement of automated control software and image recognition techniques for rapidly evaluating charge stability diagrams. We use an image analysis toolbox developed in Python to automate the calibration of virtual gates, a process that previously involved a large amount of user intervention. Moreover, we show that straightforward feedback protocols can be used to simultaneously tune multiple tunnel couplings in a triple quantum dot in a computer automated fashion. Finally, we adopt the use of a “tunnel coupling lever arm” to model the interdot barrier gate response and discuss how it can be used to more rapidly tune interdot tunnel couplings to the gigahertz values that are compatible with exchange gates.
关键词： image recognition,tunnel couplings,automated control software,virtual gates,semiconductor quantum dot devices,charge stability diagrams,quantum computing
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Towards Continuous Variables Quantum Computing with Trapped Ions
摘要： The usually employed methods of using spin states of atomic-like systems for quantum information encoding suffer from scalability issues. For example, it becomes very challenging to control a large number of trapped atomic ions each representing a physical qubit. The alternative approach would be to exploit the large Hilbert space provided by a near-harmonic trapping potential and encode the information in the oscillator states. We use sideband-resolved addressing of motional states in a single trapped 171Yb ion to demonstrate a conditional beam splitter gate. The conditional beam splitter (CBS) Hamiltonian |e??e|(a?b + ab?) swaps the quantum states of two motional modes of a trapped ion, conditioned on the ion’s internal state. It thus can be viewed as a SWAP gate and we utilize it to demonstrate SWAP tests, implement single shot parity measurements, and generate maximally entangled NOON states of motion. We discuss the spurious phase shifts that prevent the gate to be dubbed as universal and show that with an addition of an ancilla vacuum mode, the conditional beam splitter gate in trapped ion system can be used to construct a universal exponential-SWAP gate that is required for practical algorithms such as matrix inversion and other interesting applications.
关键词： SWAP gate,conditional beam splitter gate,NOON states,quantum computing,trapped ions
更新于2025-09-11 14:15:04
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Universal Photonic Quantum Interface for a Quantum Network
摘要： Active research on mesoscopic quantum systems has increased our understanding of and ability to control quantum objects, allowing the construction of a universal form for quantum networks that consist of more than one physical system. This kind of quantum network is anticipated to enable the building of quantum infrastructure, such as long-distance quantum communication and distributed quantum computers, and motivates the establishment of photonic quantum interfaces that are compatible with physical systems. Here, a universal photonic quantum interface is experimentally developed with the benefit of a unique, specially designed entangled photon source. The detailed experimental results show that this configuration can satisfy all the urgent demands for a photonic quantum interface, including the accurate matching of the working wavelength and bandwidth and specifically, the entanglement ability (F = 89.6%, S = 2.36 ± 0.03). The realization of this universal photonic quantum interface is expected to expedite the construction of much more complex quantum networks and to be a major step in the area of optical engineering and control.
关键词： photonic quantum interface,distributed quantum computing,quantum networks,entangled photon source,quantum communication
更新于2025-09-10 09:29:36