1,332 research outputs found
The non-deterministic quantum logic operation and teleportation of a vacuum and single photon superposition state via parametric amplifiers
We firstly present an all-optical scheme to implement the non-deterministic
quantum logic operation of Knill, Laflamme and Milburn (Nature, 409,
46-52(2001)). In our scheme, squeezed vacuum state is acted as auxiliary state
instead of single photon resources. Then we demonstrate that same setup can be
used to teleport a superposition of vacuum and single photon state of the form
and a superposition of vacuum and single polarized photon
state of the form .Comment: to appear in phys.Lett.
Filtration and Extraction of Quantum States from Classical Inputs
We propose using nonlinear Mach-Zehnder interferometer (NMZI) to efficiently
prepare photonic quantum states from a classical input. We first analytically
investigate the simple NMZI that can filtrate single photon state from weak
coherent state by preferrentially blocking two-photon component. As a
generalization, we show that the cascaded NMZI can deterministically extract
arbitrary quantum state from a strong coherent state. Finally, we numerically
demonstrate that the cascaded NMZI can be very efficient in both the input
power and the level of cascade. The protocol of quantum state preparation with
NMZI can be extended to various systems of bosonic modes.Comment: 5 pages, 3 figure
Chiral Symmetry Breaking in Micro-Ring Optical Cavity By Engineered Dissipation
We propose a method to break the chiral symmetry of light in traveling wave
resonators by coupling the optical modes to a lossy channel. Through the
engineered dissipation, an indirect dissipative coupling between two oppositely
propagating modes can be realized. Combining with reactive coupling, it can
break the chiral symmetry of the resonator, allowing light propagating only in
one direction. The chiral symmetry breaking is numerically verified by the
simulation of an electromagnetic field in a micro-ring cavity, with proper
refractive index distributions. This work provokes us to emphasize the
dissipation engineering in photonics, and the generalized idea can also be
applied to other systems.Comment: 6 pages, 3 figure
Reference-Based Sequence Classification
Sequence classification is an important data mining task in many real world
applications. Over the past few decades, many sequence classification methods
have been proposed from different aspects. In particular, the pattern-based
method is one of the most important and widely studied sequence classification
methods in the literature. In this paper, we present a reference-based sequence
classification framework, which can unify existing pattern-based sequence
classification methods under the same umbrella. More importantly, this
framework can be used as a general platform for developing new sequence
classification algorithms. By utilizing this framework as a tool, we propose
new sequence classification algorithms that are quite different from existing
solutions. Experimental results show that new methods developed under the
proposed framework are capable of achieving comparable classification accuracy
to those state-of-the-art sequence classification algorithms
Phonon induced spin squeezing based on geometric phase
A scheme to achieve spin squeezing using a geometric phase induced by a
single mechanical mode is proposed. The analytical and numerical results show
that the ultimate degree of spin squeezing depends on the parameter
, which is the ratio between the thermal
excitation, the quality factor and square root of ensemble size. The undesired
coupling between the spin ensemble and the bath can be efficiently suppressed
by Bang-Bang control pulses. With high quality factor, the ultimate limit of
the ideal one-axis twisting spin squeezing can be obtained for an NV ensemble
in diamond
Detuning Enhanced Cavity Spin Squeezing
The unconditionally squeezing of the collective spin of an atomic ensemble in
a laser driven optical cavity (I. D. Leroux, M. H. Schleier-Smith, and V.
Vuletic, Phys. Rev. Lett 104, 073602 (2010)) is studied and analyzed
theoretically. Surprisingly, we find that the largely detuned driving laser can
improve the scaling of cavity squeezing from to , where S
is the total atomic spin. Moreover, we also demonstrate that the experimental
imperfection of photon scattering into free space can be efficiently suppressed
by detuning.Comment: 5 pages, 3 figure
Incoherent control of electromagnetically induced transparency and Aulter-Townes splitting
The absorption and dispersion of probe light is studied in an unified
framework of three-level system, with coherent laser driving and incoherent
pumping and relaxation. The electromagnetically induced transparency (EIT) and
Autler-Townes splitting (ATS) are studied in details. In the phase diagram of
the unified three-level system, there are distinct parameter regimes
corresponding to different lineshapes and mechanisms, and the incoherent
transition could control the cross-over between EIT and ATS. The incoherent
control of the three-level system enables the investigation of various
phenomena in quantum optics, and is beneficial for experiments of light-matter
interactions.Comment: 4 pages, 4 figure
Field-induced topological pair-density wave states in a multilayer optical lattice
We study the superfluid phases of a Fermi gas in a multilayer optical lattice
system in the presence of out-of-plane Zeeman field, as well as spin-orbit (SO)
coupling. We show that the Zeeman field combined with the SO coupling leads to
exotic topological pair-density wave (PDW) phases in which different layers
possess different superfluid order parameters, even though each layer
experiences the same Zeeman field and the SO coupling. We elucidate the
mechanism of the emerging PDW phases, and characterize their topological
properties by calculating the associated Chern numbers.Comment: 7 pages, 6 figures, accepted by Phys. Rev.
Fulde-Ferrell superfluids in spinless ultracold Fermi gases
The Fulde-Ferrell (FF) superfluid phase, in which fermions form
finite-momentum Cooper pairings, is well studied in spin-singlet superfluids in
past decades. Different from previous works that engineer the FF state in
spinful cold atoms, we show that the FF state can emerge in spinless Fermi
gases confined in optical lattice associated with nearest-neighbor
interactions. The mechanism of the spinless FF state relies on the split Fermi
surfaces by tuning the chemistry potential, which naturally gives rise to
finite-momentum Cooper pairings. The phase transition is accompanied by changed
Chern numbers, in which, different from the conventional picture, the band gap
does not close. By beyond-mean-field calculations, we find the finite-momentum
pairing is more robust, yielding the system promising for maintaining the FF
state at finite temperature. Finally we present the possible realization and
detection scheme of the spinless FF state.Comment: 14 pages, 6 figure
Quantum states preparation of an atomic ensemble via cavity-assisted homodyne measurement
The quantum spin states of atomic ensemble are of special interesting for
both fundamental studies and precision measurement applications. Here, we
propose a scheme to prepare collective quantum states of an atomic ensemble
placed in an optical cavity via homodyne measurement of probing light field.
The effective interactions of atoms mediated by photons are enhanced by the
optical cavity, and the output probe light could also be entangled with the
collective spin states. By selectively measuring the quadrature of output
light, we can prepare various quantum states, including superposition states of
Dicke states and Dicke squeezed states. It is also demonstrated that the
fidelity of prepared quantum state can be enhanced by repetitive homodyne
detection and using longer probe laser pulses. Our scheme is feasible for
experimental realization with current technologies, which may be used in future
study of quantum mechanics and quantum metrology.Comment: 7 pages, 4 figure
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