1,031 research outputs found
Cavity-based architecture to preserve quantum coherence and entanglement
Quantum technology relies on the utilization of resources, like quantum
coherence and entanglement, which allow quantum information and computation
processing. This achievement is however jeopardized by the detrimental effects
of the environment surrounding any quantum system, so that finding strategies
to protect quantum resources is essential. Non-Markovian and structured
environments are useful tools to this aim. Here we show how a simple
environmental architecture made of two coupled lossy cavities enables a switch
between Markovian and non-Markovian regimes for the dynamics of a qubit
embedded in one of the cavity. Furthermore, qubit coherence can be indefinitely
preserved if the cavity without qubit is perfect. We then focus on entanglement
control of two independent qubits locally subject to such an engineered
environment and discuss its feasibility in the framework of circuit quantum
electrodynamics. With up-to-date experimental parameters, we show that our
architecture allows entanglement lifetimes orders of magnitude longer than the
spontaneous lifetime without local cavity couplings. This cavity-based
architecture is straightforwardly extendable to many qubits for scalability.Comment: 12 pages, 9 figures, 1 table. To appear on Nature Scientific Report
Harnessing non-Markovian quantum memory by environmental coupling
Controlling the non-Markovian dynamics of open quantum systems is essential
in quantum information technology since it plays a crucial role in preserving
quantum memory. Albeit in many realistic scenarios the quantum system can
simultaneously interact with composite environments, this condition remains
little understood, particularly regarding the effect of the coupling between
environmental parts. We analyze the non-Markovian behavior of a qubit
interacting at the same time with two coupled single-mode cavities which in
turn dissipate into memoryless or memory-keeping reservoirs. We show that
increasing the control parameter, that is the two-mode coupling, allows for
triggering and enhancing a non-Markovian dynamics for the qubit starting from a
Markovian one in absence of coupling. Surprisingly, if the qubit dynamics is
non-Markovian for zero control parameter, increasing the latter enables
multiple transitions from non-Markovian to Markovian regimes. These results
hold independently on the nature of the reservoirs. This work highlights that
suitably engineering the coupling between parts of a compound environment can
efficiently harness the quantum memory, stored in a qubit, based on
non-Markovianity.Comment: 8 pages, 5 figures. To appear in Phys. Rev.
Entanglement dynamics for the double Tavis-Cummings model
A double Tavis-Cummings model (DTCM) is developed to simulate the
entanglement dynamics of realistic quantum information processing where two
entangled atom-pairs and are distributed in such a way that atoms
are embedded in a cavity while are located in another remote
cavity . The evolutions of different types of initially shared entanglement
of atoms are studied under various initial states of cavity fields. The results
obtained in the DTCM are compared with that obtained in the double
Jaynes-Cummings model (DJCM) [J. Phys. B \textbf{40}, S45 (2007)] and an
interaction strength theory is proposed to explain the parameter domain in
which the so-called entanglement sudden death occurs for both the DTCM and
DJCM.Comment: 11 figure
All-optical control of thermal conduction in waveguide QED
We investigate the heat conduction between two one-dimension waveguides
intermediated by a Laser-driving atom. The Laser provides the optical control
on the heat conduction. The tunable asymmetric conduction of the heat against
the temperature gradient is realized. Assisted by the modulated Laser, the heat
conduction from either waveguide to the other waveguide can be suppressed.
Meanwhile, the conduction towards the direction opposite to the suppressed one
is gained. The heat currents can be significantly amplified by the energy flow
of the Laser. Moveover, the scheme can act like a heat engine
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