3,081 research outputs found
Determining temperature and Rabi frequency regarding trapped ions in Doppler cooling: An analytic investigation
Doppler cooling with lasers is essential to ions' trapping and also a
preliminary step towards achievement of ultracold ions. Due to lack of
effective tools, experimentally monitoring the ions' temperature and the
laser-ion coupling is difficult in Doppler cooling. Here we analytically
explore the Doppler cooling process of trapped ions, exemplified by
Ca, by solving the friction coefficient in the Doppler cooling
with respect to a thermal bath, particularly, to a bath with large heating
rate. We show four regions for cooling and heating induced by the three-level
electromagnetically induced transparency and propose a practical method for
measuring the Rabi frequency by the Doppler cooling window. In addition, the
final temperature of the laser-cooled ions can be obtained analytically in the
case of a weak thermal bath, whereas for the strong thermal bath this requires
numerical treatment due to involvement of the Doppler shift and large
Lamb-Dicke parameter. Our analytic results would help for understanding many
experimental observations, such as configuration phase transition, phonon laser
and thermodynamics regarding hot trapped ions.Comment: 10 Figure
Resonant-interaction-induced Rydberg antiblockade
Different from the conventional Rydberg antiblockade (RAB) regime that either
requires weak Rydberg-Rydberg interaction (RRI), or compensates Rydberg-Rydberg
interaction (RRI)-induced energy shift by introducing dispersive interactions,
we show that RAB regime can be achieved by resonantly driving the transitions
between ground state and Rydberg state under strong RRI. The Rabi frequencies
are of small amplitude and time-dependent harmonic oscillation, which plays a
critical role for the presented RAB. The proposed unconventional RAB regime is
used to construct high-fidelity controlled-Z (CZ) gate and controlled-not
(CNOT) gate in one step. Each atom requires single external driving. And the
atomic addressability is not required for the presented unconventional RAB,
which would simplify experimental complexity and reduce resource consumption.Comment: 5 pages, 3 figure
Steady three-dimensional dark state entanglement in dissipative Rydberg atoms
Scheme to prepare three-dimensional entangled state between a pair of Rydberg
atoms is proposed via dissipative dynamics and Electromagnetic Induced
Transparency (EIT) associated with the single-atom dark state. The prepared
entangled state is the dark state of the whole system. The schemes are feasible
no matter the system initially in arbitrary purity or mixed states and do not
have accurate requirements on evolution time. In contrast to most of the former
Rydberg-atombased dissipative schemes, the Rydberg-Rydberg interaction (RRI)
strength do not need to satisfy a certain relation with laser detuning since it
works in the blockade as well as intermediate regimes.Comment: 7 pages,9 figure
Construction of robust Rydberg controlled-phase gates
One scheme is presented to construct the robust multi-qubit arbitrary-phase
controlled-phase gate (CPG) with one control and multiple target qubits in
Rydberg atoms using the Lewis-Riesenfeld (LR) invariant method. The scheme is
not limited by adiabatic condition while preserves the robustness against
control parameter variations of adiabatic evolution. Comparing with the
adiabatic case, our scheme does not require very strong Rydberg interaction
strength. Taking the construction of two-qubit CPG as an example, our
scheme is more robust against control parameter variations than non-adiabatic
scheme and faster than adiabatic scheme.Comment: 5 pages,2 figure
Distributed quantum information processing via single atom driving
We propose an unconventional scheme for quantum entangled state distribution
(QESD) and quantum state transfer~(QST) based on a fiber-cavity-atom system, in
which three atoms are confined, respectively, in three bimodal cavities
connected with each other by optical fibers. The key feature of the scheme is
the virtual excitation of photons, which yields QESD and QST between the two
atoms in the edge-cavities conditioned on one-step operation only on the atom
in the middle cavity. No actual operation is performed on the two atoms in the
edge cavities throughout the scheme. Robustness of the scheme over operational
imperfection and dissipation is discussed and the results show that system
fidelity is always at a high level. Finally, the experimental feasibility is
justified using laboratory available values.Comment: 16pages, 8 figure
Nonadiabatic noncyclic geometric quantum computation in Rydberg atoms
Nonadiabatic geometric quantum computation (NGQC) has been developed to
realize fast and robust geometric gate. However, the conventional NGQC is that
all of the gates are performed with exactly the sameamount of time, whether the
geometric rotation angle is large or small, due to the limitation of cyclic
condition. Here, we propose an unconventional scheme, called nonadiabatic
noncyclic geometric quantum computation(NNGQC), that arbitrary single- and
two-qubit geometric gate can be constructed via noncyclic non-Abeliangeometric
phase. Consequently, this scheme makes it possible to accelerate the
implemented geometric gatesagainst the effects from the environmental
decoherence. Furthermore, this extensible scheme can be applied invarious
quantum platforms, such as superconducting qubit and Rydberg atoms.
Specifically, for single-qubit gate,we make simulations with practical
parameters in neutral atom system to show the robustness of NNGQC and also
compare with NGQC using the recent experimental parameters to show that the
NNGQC can significantly suppress the decoherence error. In addition, we also
demonstrate that nontrivial two-qubit geometric gate can berealized via
unconventional Rydberg blockade regime within current experimental
technologies. Therefore, ourscheme provides a promising way for fast and robust
neutral-atom-based quantum computation.Comment: 6 pages, 6 figures. Published visio
Preparation of three-dimensional entanglement for distant atoms in coupled cavities via atomic spontaneous emission and cavity decay
We propose a dissipative scheme to prepare a three-dimensional entangled
state for two atoms trapped in separate coupled cavities. Our work shows that
both atomic spontaneous emission and cavity decay, which are two typical
obstacles in unitary-dynamics-based schemes, could be utilized as resources for
high-dimensional entangled state preparation without specifying initial state
and controlling time precisely. Final numerical simulation with one group of
experimental parameters indicates that the performance of our scheme is better
than the unitary-dynamics-based scheme.Comment: 8 pages, 10 figure
Adiabatic passage for three-dimensional entanglement generation through quantum Zeno dynamics
We propose an adiabatic passage approach to generate two atoms three-
dimensional entanglement with the help of quantum Zeno dynamics in a time-
dependent interacting field. The atoms are trapped in two spatially separated
cavi- ties connected by a fiber, so that the individual addressing is needless.
Because the scheme is based on the resonant interaction, the time required to
generate entangle- ment is greatly shortened. Since the fields remain in vacuum
state and all the atoms are in the ground states, the losses due to the
excitation of photons and the spon- taneous transition of atoms are suppressed
efficiently compared with the dispersive protocols. Numerical simulation
results show that the scheme is robust against the decoherences caused by the
cavity decay and atomic spontaneous emission. Addi- tionally, the scheme can be
generalized to generate N-atom three-dimensional en- tanglement and
high-dimensional entanglement for two spatially separated atoms
Search for signal in single top quark production at LHC
The heavy charged gauge bosons were proposed in the theories beyond standard
model. We explore the discovery potential for with top quark
semi-leptonic decay at the LHC. We concentrate on the new physics signal search
with the deviation from the standard model prediction if the resonance peak of
can not be observed directly. The events of signal with two jets plus one
charged lepton and missing energy are simulated together with the dominant
standard model backgrounds. In this paper, it is found that suitable cuts on
the kinematic observables can effectively suppress the standard model
backgrounds, so that it is possible to search for signal at the LHC with
its mass less than 6.6 TeV.Comment: 20 pages, 14 figure
Periodically-driven facilitated high-efficiency dissipative entanglement with Rydberg atoms
A time-dependent periodical field can be utilized to efficiently modify the
Rabi coupling of system, exhibiting nontrivial dynamics. We propose a scheme to
show that this feature can be applied for speeding up the formation of
dissipative steady entanglement based on Rydberg anti-blockade mechanism in a
simplified configuration, fundamentally stemming from a frequency match between
the external-field modulation frequency and the systematic characteristic
frequency. In the presence of an optimal modulation frequency that is exactly
equal to the central frequency of driving field, it enables a sufficient
residence time of the two-excitation Rydberg state for an irreversible
spontaneous decay onto the target state, leading to an accelerated
high-fidelity steady entanglement ~0.98, with a shorter formation time <400\mu
s. We show that, a global maximal fidelity benefits from a consistence of
microwave-field coupling and spontaneous decay strengths, by which the scheme
promises a robust insensitivity to the initial population distributions. This
simple approach to facilitate the generation of dissipative entangled two-qubit
states by using periodic drivings may guide a new experimental direction in
Rydberg quantum technology and quantum information.Comment: 9 pages, 7 figures, accepted by Physical Review
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