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1.
The collective excitations of spin states of an ensemble of polar molecules are studied as a candidate for high-fidelity quantum memory. To avoid the collisional properties of the molecules, they are arranged in dipolar crystals under one or two dimensional trapping conditions. We calculate the lifetime of the quantum memory by identifying the dominant decoherence mechanisms and estimating their effects on gate operations when a molecular ensemble qubit is transferred to a microwave cavity. 相似文献
2.
Rabl P DeMille D Doyle JM Lukin MD Schoelkopf RJ Zoller P 《Physical review letters》2006,97(3):033003
We investigate a hybrid quantum circuit where ensembles of cold polar molecules serve as long-lived quantum memories and optical interfaces for solid state quantum processors. The quantum memory realized by collective spin states (ensemble qubit) is coupled to a high-Q stripline cavity via microwave Raman processes. We show that, for convenient trap-surface distances of a few microm, strong coupling between the cavity and ensemble qubit can be achieved. We discuss basic quantum information protocols, including a swap from the cavity photon bus to the molecular quantum memory, and a deterministic two qubit gate. Finally, we investigate coherence properties of molecular ensemble quantum bits. 相似文献
3.
We discuss the possibility of trapping polar molecules in the standing-wave electromagnetic field of a microwave resonant cavity. Such a trap has several novel features that make it very attractive for the development of ultracold molecule sources. Using commonly available technologies, microwave traps can be built with large depth (up to several Kelvin) and acceptance volume (up to several cm3), suitable for efficient loading with currently available sources of cold polar molecules. Unlike most previous traps for molecules, this technology can be used to confine the strong-field seeking absolute ground state of the molecule, in a free-space maximum of the microwave electric field. Such ground state molecules should be immune to inelastic collisional losses. We calculate elastic collision cross-sections for the trapped molecules, due to the electrical polarization of the molecules at the trap center, and find that they are extraordinarily large. Thus, molecules in a microwave trap should be very amenable to sympathetic and/or evaporative cooling. The combination of these properties seems to open a path to producing large samples of polar molecules at temperatures much lower than has been previously possible.Received: 30 June 2004, Published online: 23 November 2004PACS:
33.80.Ps Optical cooling of molecules; trapping - 34.50.-s Scattering of atoms and molecules - 33.80.-b Photon interactions with molecules - 33.55.Be Zeeman and Stark effects 相似文献
4.
We presented a scheme to implement SWAP gate in a microwave cavity. In our scheme, two superconducting quantum interference
device (SQUID) qubits are coupled to a single-mode microwave cavity field by adiabatic passage method for their manipulation.
This process of implementing SWAP gate is in the range of present experiments. The scheme can be easily obtained only by three
steps, which does not require perform any operation. In the scheme, the operations only involve three lowest flux states of
the SQUIDs, and the excited states would not be excited; therefore, the decoherence due to spontaneous emission of the SQUIDs’
levels would not affect the operations. In addition, during the whole procedure the cavity field is not necessary to be excited
because it does not require transfer quantum information between the SQUID’s and the cavity field. Thus, the cavity decay
is suppressed. Therefore our scheme may be realized in superconducting systems. 相似文献
5.
Born-Oppenheimer breakdown effects and hyperfine structure in the rotational spectra of SbF and SbCl
Stephen A. Cooke 《Journal of Molecular Spectroscopy》2005,234(2):195-203
Pure rotational spectra have been measured for the ground electronic states of SbF and SbCl. The molecules were prepared by laser ablation of Sb metal in the presence of SF6 or Cl2, respectively. Their spectra were measured with a cavity pulsed jet Fourier transform microwave spectrometer. Although both molecules have two unpaired electrons, they are subject to Hund’s coupling case (c), and have X10+ ground states. The spectra have been interpreted with the formalism of 1Σ+ molecules. For both molecules spectra of several isotopomers have been measured in the ground and first excited vibrational states. Large hyperfine splittings attributable to both nuclear quadrupole coupling and nuclear spin-rotation coupling have been observed. A Dunham-type analysis has produced unusually large Born-Oppenheimer breakdown parameters, which are interpreted in terms of the electronic structures of the molecules. 相似文献
6.
Liu JianFei Hou HongTao Mao DongQing Feng ZiQiang Ma ZhenYu Luo Chen Zhao ShenJie Zhao YuBin Yu HaiBo Yin Bo Zhang ZhiGang Zheng Xiang Li Zheng 《中国科学:物理学 力学 天文学(英文版)》2011,54(2):169-173
Superconducting cavities have been adopted in many kinds of accelerator facilities such as synchrotron radiation light source, hard X-ray free electron laser linac, colliders and energy recovery linacs (ERL). The 500 MHz superconducting cavities will be a candidate to be installed in the high current accelerators and high current ERLs for their large beam aperture, low higher order modes impedance and high current threshold value. This paper presents great progress in the whole sequence of developing 500 MHz superconducting cavity in China. It describes the first in-house successful development of 500 MHz single cell superconducting cavity including the deep-drawing of niobium half cells, electron beam wielding of cavity, surface preparations and vertical testing. The highest accelerating gradient of the fabricated cavity #SCD-02 higher than 10 MV/m was obtained while the quality factor was better than 4×108 at 4.2 K, which has reached the world level of the same kind of cavities. 相似文献
7.
Engineering three-dimensional maximally entangled states for two modes in a bimodal cavity
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An alternative scheme is proposed for engineering three-dimensional
maximally entangled states for two modes of a superconducting
microwave cavity. In this scheme, an appropriately prepared
four-level atom is sent through a bimodal cavity. During its passing
through the cavity, the atom is coupled resonantly with two cavity
modes simultaneously and addressed by a classical microwave pulse
tuned to the required transition. Then the atomic states are detected
to collapse two modes onto a three-dimensional maximally entangled
state. The scheme is different from the previous one in which two
nonlocal cavities are used. A comparison between them is also made. 相似文献
8.
N. S. Azaryan M. A. Baturitsky Yu. A. Budagov V. V. Glagolev D. L. Demin S. V. Kolosov A. A. Kurayev L. M. Onishchenko T. L. Popkova A. O. Rak A. K. Sinitsyn G. V. Trubnikov G. D. Shirkov N. M. Shumeiko 《Physics of Particles and Nuclei Letters》2013,10(7):788-794
A precision method for measuring of ultrahigh unloaded Q factors of superconducting cavities is proposed which is based on the excitation of oscillation in the cavity by electron beam. In this measuring, the cavity is not connected to any external microwave circuit; its unloaded Q factor is determined from the loss of electron-beam power, which can be measured with high accuracy. 相似文献
9.
10.
Computation of single-cell superconducting niobium cavity for accelerator of electrons and positrons
N. S. Azaryan M. A. Baturitsky Yu. A. Budagov V. V. Glagolev D. L. Demin I. N. Kizhlai S. V. Kolosov A. A. Kurayev T. L. Popkova A. O. Rak A. K. Sinitsyn G. V. Trubnikov G. D. Shirkov 《Physics of Particles and Nuclei Letters》2012,9(2):150-162
Computations of the accelerator section of the International Linear Collider (ILC), which consists of superconducting niobium cavities, are performed for conditions of the maximum energy transfer to electrons that travel along the cavity axis. A mathematical model and software packages are created for the computation of the electric characteristics and profile of a single-cell cavity. A computer-based synthesis of the cavity shape that yields the required electric characteristics is performed. The promising design variants of a single-cell cavity, with which a quality factor of 1010 is provided at a working frequency of 1.3 GHz, are found to optimize the construction and manufacture of a single-cell cavity. The electric characteristics of a chain of single-cell cavities are computed. 相似文献
11.
We propose to use a single mesoscopic ensemble of trapped polar molecules for quantum computing. A "holographic quantum register" with hundreds of qubits is encoded in collective excitations with definite spatial phase variations. Each phase pattern is uniquely addressed by optical Raman processes with classical optical fields, while one- and two-qubit gates and qubit readout are accomplished by transferring the qubit states to a stripline microwave cavity field and a Cooper pair box where controllable two-level unitary dynamics and detection is governed by classical microwave fields. 相似文献
12.
Nondissipative Josephson current through nanoscale superconducting constrictions is carried by spectroscopically sharp energy states, the so-called Andreev states. Although theoretically predicted almost 40 years ago, no direct spectroscopic evidence of these Andreev bound states exists to date. We propose a novel type of spectroscopy based on embedding a superconducting constriction, formed by a single-level molecule junction, in a microwave QED cavity environment. In the electron-dressed cavity spectrum we find a polariton excitation at twice the Andreev bound state energy, and a superconducting-phase-dependent ac Stark shift of the cavity frequency. Dispersive measurement of this frequency shift can be used for Andreev bound state spectroscopy. 相似文献
13.
We analyse a teleportation scheme of cavity field states. The experimental sketch discussed makes use of cavity quantum electrodynamics involving the interaction of Rydberg atoms with superconducting (micromaser) cavities as well as with classical microwave (Ramsey) cavities. In our scheme the Ramsey cavities and the atoms play the role of auxiliary systems used to teleport a field state, which is formed by a linear superposition of vacuum |∅〉 and the one-photon state |1〉, from a micromaser cavity to another. 相似文献
14.
Kotochigova S 《Physical review letters》2007,99(7):073003
We propose a mechanism to produce ultracold polar molecules with microwave fields. It converts trapped ultracold atoms into vibrationally excited molecules by a single microwave transition and entirely depends on the existence of a permanent dipole moment in the molecules. As opposed to production of molecules by photoassociation or magnetic-field Feshbach resonances, our method does not rely on properties of excited states or existence of Feshbach resonances. We determine conditions for optimal creation of polar molecules in vibrationally excited states of the ground-state potential by changing frequency and intensity of the microwave field. We also explore the possibility to produce vibrationally cold molecules by combining the microwave field with an optical Raman transition or by applying a microwave field to Feshbach molecules. The production mechanism is illustrated for KRb and RbCs. 相似文献
15.
Realization of Greenberg-Horne-Zeilinger (GHZ) and W Entangled States with Multiple Superconducting Quantum-Interference Device Qubits in Cavity QED
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An alternative scheme is proposed for generating the Greenberg-Horne-Zeilinger (GHZ) and W types of the entangled states with multiple superconducting quantum-interference device (SQUID) qubits in a single-mode microwave cavity field. In this scheme, there is no transfer of quantum information between the SQUIDs and the cavity, the cavity is always in the vacuum and thus the requirement on the quality of cavity is greatly loosened. In addition, during the process of the generation of the W entangled state, the present method does not involve a real excitation of intermediate levels. Thus, decoherence due to energy relaxation of intermediate levels is minimized. 相似文献
16.
《Comptes Rendus Physique》2012,13(5):470-479
We review the use of mechanical oscillators in circuit quantum electrodynamics. The capacitive coupling of nano-electromechanical systems with quantum bits and superconducting microwave resonators gives rise to a rich quantum physics involving electrons, photons and phonons. We focus in particular on the linear coupling between a mechanical oscillator and a microwave resonator and present the quantum dynamics that stems from the phonotonic Josephson junction. The microwave cavity turns out to be a powerful device to detect quantum phonon states and manipulate entangled states between phonons and photons. 相似文献
17.
Parametric control of a superconducting flux qubit has been achieved by using two-frequency microwave pulses. We have observed Rabi oscillations stemming from parametric transitions between the qubit states when the sum of the two microwave frequencies or the difference between them matches the qubit Larmor frequency. We have also observed multiphoton Rabi oscillations corresponding to one- to four-photon resonances by applying single-frequency microwave pulses. The parametric control demonstrated in this work widens the frequency range of microwaves for controlling the qubit and offers a high quality testing ground for exploring nonlinear quantum phenomena of macroscopically distinct states. 相似文献
18.
《Physics letters. A》1999,260(5):424-428
The relative change of the microwave surface resistance has been measured as a function of temperature in the superconducting and normal states of UPt3 using a cavity perturbation technique. With our frequency range of ∼9–38 GHz, the microwave photon energy (ℏω) is ∼20–95% of the estimated zero-temperature (BCS) energy gap (2Δ0) of UPt3. The surface resistance shows a change in slope as the signature of Tc and has a significantly weaker temperature dependence in the superconducting state than would be predicted by the Mattis–Bardeen theory. At higher frequencies, the slope tends to change by a smaller amount. No indication of collective modes at any of the frequencies was observed down to the lowest temperatures measured (∼0.1 K). 相似文献
19.
《Comptes Rendus Physique》2016,17(7):729-739
The techniques of microwave quantum optics are applied to collective spin excitations in a macroscopic sphere of a ferromagnetic insulator. We demonstrate, in the single-magnon limit, strong coupling between a magnetostatic mode in the sphere and a microwave cavity mode. Moreover, we introduce a superconducting qubit in the cavity and couple the qubit with the magnon excitation via the virtual photon excitation. We observe the magnon–vacuum-induced Rabi splitting. The hybrid quantum system enables generation and characterization of non-classical quantum states of magnons. 相似文献
20.
We present a scheme to realize the basic two-qubit logic gates such as the
quantum phase gate and SWAP gate using a detuned microwave cavity
interacting with three-level superconducting-quantum-interference-device
(SQUID) qubit(s), by placing SQUID(s) in a two-mode microwave cavity and
using adiabatic passage methods. In this scheme, the two logical states of
the qubit are represented by the two lowest levels of the SQUID, and the
cavity fields are treated as quantized. Compared with the previous method,
the complex procedures of adjusting the level spacing of the SQUID and
applying the resonant microwave pulse to the SQUID to create transformation
are not required. Based on superconducting device with relatively long
decoherence time and simplified operation procedure, the gates operate
at a high speed, which is important in view of decoherence. 相似文献