- 标题
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- 实验方案
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-SiC
摘要： The ?ne-structure splitting in zero magnetic ?eld allows one to access the coherent control and manipulation of polarized spin states. Here the zero-?eld splitting (ZFS) of the S = 3/2 silicon vacancy-related centers in 6H-SiC is explored by means of electron paramagnetic resonance and electron nuclear double resonance techniques, combined with ?rst-principle calculations. We show that the centers not only possess signi?cantly different absolute values of ZFS, but they also differ in their sign. This diversity is rationalized by a ?attened/elongated character of their spin-density distribution, potentially alters spin-photon entanglement, and suggests these centers for qubits in the upcoming technology of quantum communication and quantum-information processing.
关键词： quantum-information processing,electron paramagnetic resonance,electron nuclear double resonance,zero-?eld splitting,silicon vacancies,6H-SiC,quantum communication
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) - Controlling Light Polarization from Helical Travelling-Wave Nanoantennas
摘要： Light polarization is a key factor of modern photonics. Tailoring surface plasmons (SPs) in anisotropically-shaped metallic nanostructures introduces the prospect of polarization control at small scale [1]. However, the resulting components remain much larger than the wavelength of light. Here, we present a travelling-wave helical plasmonic antenna (TW-HPA) that overcomes this limit [2]. Due to its non-resonant nature, it differs from existing helical plasmonic structures [3-5], thus extending the concept of travelling-wave helical antenna [6] to optics. Our TW-HPA consists of a narrow gold-coated wire wound up in a screw-like shape forming a tiny helix (Fig. 1a). The gold-coated wire sustains a cutoff-free axially symmetric travelling SPs [7], locally excited with the dipolar mode of a rectangular aperture nanoantenna right at the helix's pedestal. In the course of propagation, the plasmon wire mode acquires orbital angular momentum (OAM). Due to the sharp curvatures, the OAM of the SP mode match the spin angular momentum (SAM) of free-space propagating photons [8]. On the basis of this OAM-to-SAM transfer, individual TW-HPA can produce circularly polarized directional light on the subwavelength scale through a swirling-plasmon effect. Such TW-HPAs can then be closely packed to build micron scale arrangements of tiny circularly polarized light sources of desired handedness and tunable intensities, which could open new perspectives in a large panel of photonic applications requiring local addressing, such as detectors, displays, optomagnetic recording as well as quantum information. By optically coupling four TW-HPAs of opposite handedness (Fig.1b), we obtained a phase plate occupying a volume smaller than a cubic wavelength whose polarization properties have never previously been demonstrated. Switching between left and right circular polarizations (LCP and RCP) occurs when the incident linear polarization is rotated by an angle of 52°, instead of 90° as for standard quarter wave plates. Based on the spin-orbit interaction of light, our method is versatile, robust and leads to ultracompact plasmonic polarizers and unconventional phase plates. Taken as individual or coupled structures, TW-PHAs may pave the way towards highly integrated polarization-encoded optics, particularly for the generation and control of spin-encoded photon qubits in quantum information and optical spintronics.
关键词： Light polarization,orbital angular momentum,surface plasmons,circularly polarized light,optical spintronics,quantum information,spin angular momentum,helical travelling-wave nanoantennas
更新于2025-09-11 14:15:04
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Controlled Joint Remote Preparation of a Six-Qubit Cluster-Type State by Using GHZ States
摘要： A scheme for the controlled joint remote preparation of an arbitrary six-qubit cluster-type state by using only two sets of five-qubit GHZ states as quantum channel is proposed. In our scheme, Alice firstly performs two sets of two-qubit projective measurement according to the real coefficients and the complex coefficients of the desired six-qubit cluster-type state. Then, the controller Charlie must apply another two-qubit projective measurement according to the Alice’s measurement result. Finally, Bob can obtain the desired six-qubit cluster-type state according to an appropriate unitary operation. Our scheme can achieve unit success probability.
关键词： Six-qubit cluster-type state,Quantum information,Controlled joint remote preparation
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) - A Ps-Pulse Laser for Ultrafast Entanglement Generation at 42.66 Ghz Repetition Rate
摘要： Entangled-photon sources are a key element for most quantum-information applications, ranging from quantum communication systems to quantum simulators and full photonic quantum computers. Spontaneous parametric downconversion (SPDC), requiring a pump laser and a nonlinear medium, is up-to-date still the preferred technique to generate such photonic entanglement. To scale the transmission rates or gate operations of the aforementioned applications, high clock rates of the pump lasers are needed. Moreover, photonic quantum-processing algorithms require photons with not only high entanglement visibility but also high spectral indistinguishability and purity. This can either be achieved by narrow spectral filtering, costly in rate, or by suitable choice of the pump pulse length (typically in the ps range). Attempts have been made to increase the rate of conventional fs-lasers by adding multiple spatial-paths [1] but this method cannot be used to go beyond GHz repetition rates. This results in the quest to produce pump lasers with very high repetition rate, ps-pulse width and high enough power to drive the weak SPDC process. We report here on an implementation of a compact and fast ps-pump laser setup which can generate entangled photon pairs at repetition rates up to 42.66 GHz. Our entangled-photon source can be operated at these high generation rates and is basically only limited by the jitter of the detectors. In addition, we achieve a high spectral purity without narrow bandpass-filtering by mutually matching the length of the PDC crystal and the pump laser‘s pulse length [2], yielding polarisation-entangled photon pairs with minimal spectral correlations. The pump laser consists of a monolithically integrated mode locked DBR laser emitting pulses with a fixed repetition rate of 42.66 GHz at 1554 nm with 1.8 ps length. A pulse picker, made of an intensity modulator and driven by the same controller as the pump laser, allows adjusting the repetition rate used in the experiment, as depicted in Fig. 1. The power of the laser pulses is boosted with a series of optical amplifiers to 25 dBm. Conversion to the proper wavelength for the PDC process takes place in a second-harmonic-generation module, which finally generates output pulses of (cid:79)=777 nm to pump the entangled-photon source. Our entanglement source is based on a Sagnac-interferometer, where a ppKTP crystal is pumped by two pulsed laser beams from opposed directions. The generated photon pair at 1554 nm is split into different spatial modes by a polarizing beamsplitter, collected in optical fibers and detected with InGaAs detectors (10% efficiency). An experimental analysis of the entangled polarisation state yields an average visibility of 0.95 ± 0.01, corresponding to a CHSH parameter of S=2.685 which is in good agreement with theoretical calculations. Two-photon interference based on the Hong-Ou-Mandel effect also shows a high degree of purity.
关键词： ppKTP crystal,quantum-information applications,high clock rates,Sagnac-interferometer,InGaAs detectors,entangled-photon sources,ps-pump laser,spectral purity,spontaneous parametric downconversion
更新于2025-09-11 14:15:04
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Towards a rational design of laser-coolable molecules: insights from equation-of-motion coupled-cluster calculations
摘要： Access to cold molecules is critical for quantum information science, design of new sensors, ultracold chemistry, and search of new phenomena. These applications depend on the ability to laser-cool molecules. Rigorous theory and qualitative models can play a central role in narrowing down the vast pool of potential candidates amenable to laser cooling. We report a systematic study of structural and optical properties of alkaline earth metal derivatives in the context of their applicability in laser cooling using equation-of-motion coupled-cluster methods. To rationalize and generalize the results from high-level electronic structure calculations, we develop an effective Hamiltonian model. The model explains the observed trends and suggests new principles for the design of laser-coolable molecules.
关键词： laser cooling,alkaline earth metal derivatives,effective Hamiltonian model,quantum information science,equation-of-motion coupled-cluster methods,ultracold chemistry
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) - Compact Femtosecond Laser Direct Written Integrated Retarders Based on Embedded Nanogratings
摘要： Femtosecond Laser Direct Writing (FLDW) is a well-known rapid prototyping method to fabricate integrated optical circuits in glass chips. These circuits have been used to show various quantum information applications, using the states of photons as qubits. Generally, when transmitting information via single photons, it is desirable to make use of all possible degrees of freedom that this photon has to offer, in order to increase the amount of information transferred per photon. One of these degrees of freedom is the photon’s polarization. To make use of this degree of freedom, devices capable of manipulating the polarization are required. Various approaches for manipulating the polarization of photons in a FLDW circuit have been demonstrated before, of which some were used for quantum information applications. In our work, we present a novel method of polarization control using embedded nanogratings as waveplates. These nanogratings are highly birefringent self-assembled structures. Due to their relatively high form birefringence on the order of Δn = 10^-3, they can be used as a compact waveplate enabling further miniaturization of integrated optical circuits. The properties of these gratings can be altered by using different laser parameters during the inscription process. We have added various waveplates made of nanogratings into FLDW waveguides. We demonstrate their functionality as waveplates of different retardation and optical axis orientations using crossed polarizer birefringence measurements. Due to the chosen writing geometry, a full control over the direction of the optical axis can be achieved. The thickness of these structures is on the order of a few hundred micrometers. Former approaches for polarization control in FLDW circuits required structures in the range of millimetres to centimeters. Some of these approaches were limited in the achievable optical axis orientations. Our waveplates can be both used for classical applications and as single qubit quantum gates, which will be demonstrated. Waveplate structures usable as Hadamard, Pauli-x, Pauli-z and Pi/8th gates have been fabricated. The transferability to fibers will be discussed.
关键词： integrated optical circuits,polarization control,quantum information applications,waveplates,nanogratings,Femtosecond Laser Direct Writing
更新于2025-09-11 14:15:04
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Optomagnetic plasmonic nanocircuits
摘要： The coupling between solid-state quantum emitters and nanoplasmonic waveguides is essential for the realization of integrated circuits for various quantum information processing protocols, communication, and sensing. Such applications benefit from a feasible, scalable and low loss fabrication method as well as efficient coupling to nanoscale waveguides. Here, we demonstrate optomagnetic plasmonic nanocircuitry for guiding, routing and processing the readout of electron spins of nitrogen vacancy centres. This optimized method for the realization of highly efficient and ultracompact plasmonic circuitry is based on enhancing the plasmon propagation length and improving the coupling efficiency. Our results show 5 times enhancement in the plasmon propagation length using (3-mercaptopropyl) trimethoxysilane (MPTMS) and 5.2 times improvement in the coupling efficiency by introducing a grating coupler, and these enable the design of more complicated nanoplasmonic circuitries for quantum information processing. The integration of efficient plasmonic circuitry with the excellent spin properties of nitrogen vacancy centres can potentially be utilized to extend the applications of nanodiamonds and yield a great platform for the realization of on-chip quantum information networks.
关键词： nitrogen vacancy centres,plasmon propagation length,nanoplasmonic waveguides,quantum information processing,coupling efficiency
更新于2025-09-11 14:15:04
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Optimal measurement strategies for the trine states with arbitrary prior probabilities
摘要： We investigate the optimal measurement strategy for state discrimination of the trine ensemble of qubit states prepared with arbitrary prior probabilities. Our approach generates the minimum achievable probability of error and also the maximum confidence strategy. Although various cases with symmetry have been considered and solution techniques put forward in the literature, to our knowledge this is only the second such closed form, analytical, arbitrary prior, example available for the minimum-error figure of merit, after the simplest and well-known two-state example.
关键词： quantum measurement,quantum communication,quantum information
更新于2025-09-10 09:29:36
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Cryogenic Characterization of 22nm FDSOI CMOS Technology for Quantum Computing ICs
摘要： An approach is proposed to realize large-scale, “high-temperature” and high-fidelity quantum computing ICs based on single- and multiple coupled quantum-dot electron- and hole-spin qubits monolithically integrated with the mm-wave spin manipulation and readout circuitry technology. Measurements of minimum-size 6nmx20nmx80nm Si-channel n-MOSFETs (electron-spin qubit), SiGe-channel p-MOSFETs (hole-spin qubit), and double quantum-dot complementary qubits reveal strong quantum effects in the subthreshold region at 2 K, characteristic of resonant tunneling in a quantum dot. S-parameter measurements of a transimpedance amplifier (TIA) for spin readout show improved performance from 300 K to 2 K. Finally, the qubit-with-TIA circuit has 50Ω output impedance, 78dBΩ transimpedance gain with unity-gain bandwidth of 70 GHz and consumes 3.1 mW.
关键词： CMOS,silicon-on-insulator,quantum information processing,radio frequency,monolithic integrated circuits,semiconductor quantum dots,silicon,cryogenics
更新于2025-09-10 09:29:36
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Bunching and antibunching in four wave mixing NV center in diamond
摘要： The determination of classical and quantum states through photon bunching and anti-bunching like phenomena may have potential applications in quantum information processing and long-distance quantum communications. We report the photon bunching and multi anti-bunching like phenomena by generating multi-order ?uorescence and four-wave mixing (FWM) at room temperature using the Nitrogen-vacancy (NV) center in diamond. We have implied FWM process to demonstrate the interference pattern emerging from NV of nano-crystals in classical, nonclassical and intermediate (classical and nonclassical) regimes. Intersystem crossing is controlled by the ?uence of incident beams. The interference pattern from dominant ionization of NV- to NVo and NVo to NV- suggests the bunching and anti-bunching like phenomena of photons, respectively.
关键词： antibunching,quantum information processing,quantum communications,diamond,four-wave mixing,photon bunching,NV center
更新于2025-09-10 09:29:36