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Reduction of charge impurities in a silicon metal-oxide-semiconductor quantum dot qubit device patterned with nano-imprint lithography
摘要： The silicon metal-oxide-semiconductor quantum dot architecture is a leading approach for the physical implementation of semiconductor quantum computing. One major challenge for scalable quantum dots is the presence of charge impurities. Electron-beam lithography (EBL), almost universally used to fabricate quantum dot devices, is known to create such defects at the Si/SiO2 interface. To eliminate the need for EBL, we have transferred the metal gate pattern of a quantum dot onto the silicon substrate using nano-imprint lithography. Critical features with 50 nm scale and separation can be dependably reproduced. By characterizing the bias-dependent charge transport through a quantum point contact barrier, the prevalence of impurities is found to be largely diminished in nano-imprinted devices when compared to similar electron-beam-written counterparts. High-quality charge transport and charge sensing of several quantum dots are obtained. Additionally, gate noise is measured with an average of 1.5 μeV Hz?1/2 equivalent to previous measurements made on devices fabricated with EBL, which suggests that the leading source of impurities produced by EBL are deep, ?xed charges. This work offers a path toward reliable quantum dot operation in MOS by improving fabrication techniques to reduce charge impurities.
关键词： silicon metal–insulator–semiconductor,nano-imprint lithography,quantum dot,qubit,quantum information
更新于2025-09-23 15:19:57
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[IEEE 2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS) - Shenzhen, China (2019.11.25-2019.11.27)] 2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS) - A Comparative Study of the Lifetimes of High-End and Low-Cost Off-Line LED Drivers Under Accelerated Test Conditions
摘要： In this paper, we present the following quantum compression protocol ‘P ’: Let ρ, σ be quantum states, such that S (ρ(cid:2)σ ) def= Tr(ρ log ρ ? ρ log σ ), the relative entropy between ρ and σ , is finite. Alice gets to know the eigendecomposition of ρ. Bob gets to know the eigendecomposition of σ . Both Alice and Bob know S (ρ(cid:2)σ ) and an error parameter ε. Alice and Bob use shared entanglement and after communication of O((S(ρ(cid:2)σ ) + 1)/ε4) bits from Alice to Bob, Bob ends up with a quantum state ?ρ, such that F(ρ, ?ρ) ≥ 1 ? 5ε, where F(·) represents fidelity. This result can be considered as a non-commutative generalization of a result due to Braverman and Rao where they considered the special case when ρ and σ are classical probability distributions (or commute with each other) and use shared randomness instead of shared entanglement. We use P to obtain an alternate proof of a direct-sum result for entanglement assisted quantum one-way communication complexity for all relations, which was first shown by Jain et al.. We also present a variant of protocol P in which Bob has some side information about the state with Alice. We show that in such a case, the amount of communication can be further reduced, based on the side information that Bob has. Our second result provides a quantum analog of the widely used classical correlated-sampling protocol. For example, Holenstein used the classical correlated-sampling protocol in his proof of a parallel-repetition theorem for two-player one-round games.
关键词： quantum communication complexity,compression protocols,correlated sampling,Quantum information theory,direct sum results
更新于2025-09-23 15:19:57
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Photon-added entangled Baruta??Girardello coherent states: non-classicality and generation
摘要： In continuation of previous papers where the addition of photons into the two-mode entangled quantum states was studied, we proposed a scheme to establish and generate photon-added ‘entangled Barut–Girardello coherent states’ (PAEBGCSs), by applying photon creation operators on the two-mode EBGCSs, where the latter is introduced by Hach et al. (JOSA B 35:2433, 2018), as a new class of quantum states connected to the simple harmonic oscillator and generated through a Mach–Zehnder interferometer, and the dynamics of their entanglement is analyzed in details. In addition, the EBGCSs include strong non-classical properties; then, to gain insight into the effectiveness of photon addition to them and comparing with the case already discussed as the photon-added entangled Klauder–Perelomov coherent states, we present a general analysis of non-classical properties such as photon statistics and squeezing and photon number distribution. We also derive the concurrence measure to quantify the entanglement of these states and look for conditions that provide information on whether these become maximally entangled. We show that the photon addition plays an important role in non-classical effects, and this operation can be applied to enhance the entanglement of the PAEBGCSs. For instance, entanglement preserving against quantum polarization is occurred by adding photons to the EBGCSs. Finally, an experimental procedure for generating the PAEBGCSs in the framework of cavity quantum electrodynamics is established.
关键词： non-classicality,quantum optics,Photon-added entangled Barut–Girardello coherent states,generation,quantum information
更新于2025-09-23 15:19:57
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General Quantum Entanglement Purification Protocol using a Controlleda??Phasea??Flip Gate
摘要： Entanglement purification is an important method to guarantee the fidelity of long-distance quantum communication. Here, a general entanglement purification protocol (EPP) for mixed state with bit-flip error and phase-flip error is proposed, resorting to unilateral operations and a controlled-phase-flip (CPF) gate. The CPF gate is working with a high fidelity under balance condition of quantum dot embedded in a double-sided optical cavity. This general EPP scheme can purify the mixed state with both bit-flip error and phase-flip error to a high fidelity entangled state relatively fast in some regimes, owing to the unilateral operations and high-fidelity CPF gate, which can largely decrease the resource consumption. This general EPP provides a convenient way for increasing the entanglement of different quantum systems, which has great potential for guaranteeing the fidelity of long-distance quantum communication in the future.
关键词： entanglement purification,quantum information,controlled-phase-flip gate
更新于2025-09-23 15:19:57
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Laser field control of subradiant states of a system of several atoms in a configuration close to a regular polygon
摘要： Some collective excitations of an ensemble of closely spaced (two-level) atoms can be characterised by extremely low rates of radiation decay, which is of considerable interest for storing quantum information. Such (dark) states are realised, for example, in planar geometry when atoms are located at the nodes of a regular polygon. However, the decay rate of such excitations increases markedly when the geometry deviates from ideal. Using the example of small deformation of a square in a rhombus, we show that an increase in the decay rate of the dark state due to symmetry breaking can be compensated for by adjusting the transition frequency of some atoms exposed to external laser radiation.
关键词： spontaneous decay,quantum information,subradiative states,atomic ensembles
更新于2025-09-23 15:19:57
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High Quality Entangled Photon Pair Generation in Periodically Poled Thin-Film Lithium Niobate Waveguides
摘要： A thin-film periodically poled lithium niobate waveguide was designed and fabricated which generates entangled photon pairs at telecommunications wavelengths with high coincidences-to-accidentals counts ratio CAR > 67000, two-photon interference visibility V > 99%, and heralded single-photon autocorrelation g(0) < 0.025. Nondestructive in situ diagnostics were used to determine the poling quality in 3D. Megahertz rates of photon pairs were generated by less than a milliwatt of pump power, simplifying the pump requirements and dissipation compared to traditional spontaneous parametric down-conversion lithium niobate devices.
关键词： lithium niobate waveguides,quantum information processing,entangled photon pairs,telecommunications wavelengths
更新于2025-09-23 15:19:57
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Quantum information capsule and information delocalization by entanglement in multiple-qubit systems
摘要： Where do entangled multiple-qubit systems store information? For information injected into a qubit, this question is nontrivial and interesting since the entanglement delocalizes the information. So far, a common picture is that of a qubit and its purification partner sharing the information quantum mechanically. Here, we introduce a new picture of a single qubit in the correlation space, referred to as quantum information capsule (QIC), confining the information perfectly. This picture is applicable for the entangled multiple-qubit system in an arbitrary state. Unlike the partner picture, in the QIC picture, by swapping the single-body state, leaving other subsystems untouched, the whole information can be retrieved out of the system. After the swapping process, no information remains in the system.
关键词： Quantum information,Quantum memory,Black hole information loss problem,Quantum entanglement
更新于2025-09-19 17:15:36
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Longer distance continuous variable quantum key distribution protocol with photon subtraction at the receiver
摘要： One of the limitations of continuous variable quantum key distribution is the relatively short transmission distance of secure keys. Some solutions have been proposed to overcome the limitation including reverse reconciliation, trusted noise concept, and non-Gaussian operation. In this paper, we propose a protocol using photon subtraction at the receiver, which combines the synergetic benefits of the aforementioned approaches. Using simulations, we show that the performance of the proposed protocol outperforms other conventional protocols. The results showed that an improvement in secure key distance can be obtained using a non-Gaussian operation, depending on the position where the operation is performed, similar to the trusted noise concept. Furthermore, the result implies existence of some Gaussian operations which increases security without using a beam splitter.
关键词： Continuous variable quantum key distribution,Quantum cryptography,Quantum information and processing,Non-Gaussian state
更新于2025-09-19 17:15:36
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Pattern Recognition Techniques for Boson Sampling Validation
摘要： The difficulty of validating large-scale quantum devices, such as boson samplers, poses a major challenge for any research program that aims to show quantum advantages over classical hardware. Towards this aim, we propose a novel data-driven approach, wherein models are trained to identify common pathologies using unsupervised machine-learning methods. We illustrate this idea by training a classifier that exploits K-means clustering to distinguish between boson samplers that use indistinguishable photons from those that do not. We tune the model on numerical simulations of small-scale boson samplers and then validate the pattern-recognition technique on larger numerical simulations as well as on photonic chips in both traditional boson-sampling and scatter-shot experiments. The effectiveness of such a method relies on particle-type-dependent internal correlations present in the output distributions. This approach performs substantially better on the test data than previous methods and underscores the ability to further generalize its operation beyond the scope of the examples that it was trained on.
关键词： Quantum Information,Computational Physics,Photonics
更新于2025-09-19 17:15:36
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Long-distance entangling gates between quantum dot spins mediated by a superconducting resonator
摘要： Recent experiments with silicon qubits demonstrated strong coupling of a microwave resonator to the spin of a single electron in a double quantum dot, opening up the possibility of long-range spin-spin interactions. We present our theoretical calculation of effective interactions between distant quantum dot spins coupled by a resonator, and propose a protocol for fast, high-fidelity two-qubit gates consistent with experimentally demonstrated capabilities. Our simulations show that, in the presence of noise, spin-spin entangling gates significantly outperform cavity-mediated gates on charge qubits.
关键词： superconducting resonator,entangling gates,quantum dot spins,quantum information processing
更新于2025-09-19 17:13:59