1,985 research outputs found
Selective-Resonance-Based Quantum Entangling Operation on Qubits in Circuit QED
We present a fast quantum entangling operation on superconducting qubits
assisted by a resonator in the quasi-dispersive regime with a new effect ---
the selective resonance coming from the amplified qubit-state-dependent
resonator transition frequency and the tunable period relation between a wanted
quantum Rabi oscillation and an unwanted one. This operation does not require
any kind of drive fields and the interaction between qubits. More interesting,
the non-computational third excitation states of the charge qubits can play an
important role in shortening largely the operation time of the entangling
gates. All those features provide an effective way to realize much faster
quantum entangling gates on superconducting qubits than previous proposals.Comment: 5 pages, 4 figure
Quantum state transfer and controlled-phase gate on one-dimensional superconducting resonators assisted by a quantum bus
We propose a quantum processor for the scalable quantum computation on
microwave photons in distant one-dimensional superconducting resonators. It is
composed of a common resonator R acting as a quantum bus and some distant
resonators coupled to the bus in different positions assisted by
superconducting quantum interferometer devices (SQUID), different from previous
processors. R is coupled to one transmon qutrit, and the coupling strengths
between and R can be fully tuned by the external flux through the SQUID.
To show the processor can be used to achieve universal quantum computation
effectively, we present a scheme to complete the high-fidelity quantum state
transfer between two distant microwave-photon resonators and another one for
the high-fidelity controlled-phase gate on them. By using the technique for
catching and releasing the microwave photons from resonators, our processor may
play an important role in quantum communication as well.Comment: 11 pages, 4 figures, one colum
Fast universal quantum gates on microwave photons with all-resonance operations in circuit QED
Stark shift on a superconducting qubit in circuit quantum electrodynamics
(QED) has been used to construct universal quantum entangling gates on
superconducting resonators in previous works. It is a second-order coupling
effect between the resonator and the qubit in the dispersive regime, which
leads to a slow state-selective rotation on the qubit. Here, we present two
proposals to construct the fast universal quantum gates on superconducting
resonators in a microwave-photon quantum processor composed of multiple
superconducting resonators coupled to a superconducting transmon qutrit, that
is, the controlled-phase (c-phase) gate on two microwave-photon resonators and
the controlled-controlled phase (cc-phase) gates on three resonators, resorting
to quantum resonance operations, without any drive field. Compared with
previous works, our universal quantum gates have the higher fidelities and
shorter operation times in theory. The numerical simulation shows that the
fidelity of our c-phase gate is 99.57% within about 38.1 ns and that of our
cc-phase gate is 99.25% within about 73.3 ns.Comment: 12 pages, 6 figures, 2 table
Universal quantum gates on microwave photons assisted by circuit quantum electrodynamics
Based on a microwave-photon quantum processor with two superconducting
resonators coupled to one transmon qutrit, we construct the controlled-phase
(c-phase) gate on microwave-photon-resonator qudits, by combination of the
photon-number-dependent frequency-shift effect on the transmon qutrit by the
first resonator and the resonant operation between the qutrit and the second
resonator. This distinct feature provides us a useful way to achieve the
c-phase gate on the two resonator qudits with a higher fidelity and a shorter
operation time, compared with the previous proposals. The fidelity of our
c-phase gate can reach 99.51% within 93 ns. Moreover, our device can be
extended easily to construct the three-qudit gates on three resonator qudits,
far different from the existing proposals. Our controlled-controlled-phase gate
on three resonator qudits is accomplished with the assistance of a transmon
qutrit and its fidelity can reach 92.92% within 124.64 ns.Comment: 9 pages, 5 figure
One-step implementation of entanglement generation on microwave photons in distant 1D superconducting resonators
We present a scalable quantum-bus-based device for generating the
entanglement on microwave photons (MPs) in distant superconducting resonators
(SRs). Different from the processors in previous works with some resonators
coupled to a superconducting qubit (SQ), our device is composed of some 1D SRs
which are coupled to the quantum bus (another common resonator ) in
its different positions simply, assisted by superconducting quantum
interferometer devices. By using the technique for catching and releasing a MP
state in a 1D SR, it can work as an entanglement generator or a node in quantum
communication. To demonstrate the performance of this device, we propose a
one-step scheme to generate high-fidelity Bell states on MPs in two distant
SRs. It works in the dispersive regime of and , which enables us to
extend it to generate high-fidelity multi-Bell states on different resonator
pairs simultaneously.Comment: 5 pages, 3 figure
Quantum information processing on nitrogen-vacancy ensembles with the local resonance assisted by circuit QED
With the local resonant interaction between a nitrogen-vacancy-center
ensemble (NVE) and a superconducting coplanar resonator, and the single-qubit
operation, we propose two protocols for the state transfer between two remote
NVEs and for fast controlled-phase (c-phase) on these NVEs, respectively. This
hybrid quantum system is composed of two distant NVEs coupled to separated
high-Q transmission line resonators (TLRs), which are interconnected by a
current-biased Josephsonjunction superconducting phase qubit. The fidelity of
our state-transfer protocol is about 99.65% within the operation time of 70.60
ns. The fidelity of our c-phase gate is about 98.23% within the operation time
of 93.87 ns. Furthermore, using the c-phase gate, we construct a
two-dimensional cluster state on NVEs in n*n square grid based on the hybrid
quantum system for the one-way quantum computation. Our protocol may be more
robust, compared with the one based on the superconducting resonators, due to
the long coherence time of NVEs at room temperature.Comment: 10 pages, 4 figure
Universal distributed quantum computing on superconducting qutrits with dark photons
We present a one-step scheme to construct the controlled-phase gate
deterministically on remote transmon qutrits coupled to different resonators
connected by a superconducting transmission line for an universal distributed
quantum computing. Different from previous works on remote superconducting
qubits, the present gate is implemented with coherent evolutions of the entire
system in the all-resonance regime assisted by the dark photons to robust
against the transmission line loss, which allows the possibility of the complex
designation of a long-length transmission line to link lots of circuit QEDs.
The length of the transmission line can reach the scale of several meters,
which makes our scheme is suitable for the large-scale distributed quantum
computing. This gate is a fast quantum entangling operation with a high
fidelity of about 99%. Compare with previous works in other quantum systems for
a distributed quantum computing, under the all-resonance regime, the present
proposal does not require classical pulses and ancillary qubits, which relaxes
the difficulty of its implementation largely.Comment: 10 pages, 4 figures, one colum
Complete hyperentangled-Bell-state analysis for photon systems assisted by quantum-dot spins in optical microcavities
Bell-state analysis (BSA) is essential in quantum communication, but it is
impossible to distinguish unambiguously the four Bell states in the
polarization degree of freedom (DOF) of two-photon systems with only linear
optical elements, except for the case in which the BSA is assisted with
hyperentangled states, the simultaneous entanglement in more than one DOF.
Here, we propose a scheme to distinguish completely the 16 hyperentangled Bell
states in both the polarization and the spatial-mode DOFs of two-photon
systems, by using the giant nonlinear optics in quantum dot-cavity systems.
This scheme can be applied to increase the channel capacity of long-distance
quantum communication based on hyperentanglement, such as entanglement
swapping, teleportation, and superdense coding. We use hyperentanglement
swapping as an example to show the application of this HBSA.Comment: 11 pages (in one column), 5 figure
High-efficiency multipartite entanglement purification of electron-spin states with charge detection
We present a high-efficiency multipartite entanglement purification protocol
(MEPP) for electron-spin systems in a Greenberger-Horne-Zeilinger state based
on their spins and their charges. Our MEPP contains two parts. The first part
is our normal MEPP with which the parties can obtain a high-fidelity N-electron
ensemble directly, similar to the MEPP with controlled-not gates. The second
one is our recycling MEPP with entanglement link from N'-electron subsystems (2
< N' < N). It is interesting to show that the N'-electron subsystems can be
obtained efficiently by measuring the electrons with potential bit-flip errors
from the instances which are useless and are just discarded in all existing
conventional MEPPs. Combining these two parts, our MEPP has the advantage of
the efficiency higher than other MEPPs largely for electron-spin systems.Comment: 15 pages, 5 figure
Systematic study of decay for odd- nuclei within a two-potential approach
decay is usually associated with both ground and low-lying isomeric
states of heavy and superheavy nuclei, and the unpaired nucleon plays a key
role on decay. In this work, we systematically studied the
decay half-lives of odd- nuclei, including both favored and unfavored
decay within the two-potential approach based on the isospin dependent
nuclear potential. The preformation probabilities are estimated by
using an analytic formula taking into account the shell structure and
proton-neutron correlation, and the parameters are obtained through the
decay half-lives data. The results indicate that in general the
preformation probabilities of even-, odd- nuclei are slightly
smaller than the odd-, even- ones. We found that the odd-even staggering
effect may play a more important role on spontaneous fission than
decay. The calculated half-lives can well reproduce the experimental data
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