265 research outputs found
Digital-analog quantum simulation of generalized Dicke models with superconducting circuits
We propose a digital-analog quantum simulation of generalized Dicke models
with superconducting circuits, including Fermi-Bose condensates, biased and
pulsed Dicke models, for all regimes of light-matter coupling. We encode these
classes of problems in a set of superconducting qubits coupled with a bosonic
mode implemented by a transmission line resonator. Via digital-analog
techniques, an efficient quantum simulation can be performed in
state-of-the-art circuit quantum electrodynamics platforms, by suitable
decomposition into analog qubit-bosonic blocks and collective single-qubit
pulses through digital steps. Moreover, just a single global analog block would
be needed during the whole protocol in most of the cases, superimposed with
fast periodic pulses to rotate and detune the qubits. Therefore, a large number
of digital steps may be attained with this approach, providing a reduced
digital error. Additionally, the number of gates per digital step does not grow
with the number of qubits, rendering the simulation efficient. This strategy
paves the way for the scalable digital-analog quantum simulation of many-body
dynamics involving bosonic modes and spin degrees of freedom with
superconducting circuits.Comment: Published version, with added reference
Ultrastrong coupling phenomena beyond the Dicke model
We study effective light-matter interactions in a circuit QED system
consisting of a single resonator, which is coupled symmetrically to
multiple superconducting qubits. Starting from a minimal circuit model, we
demonstrate that in addition to the usual collective qubit-photon coupling the
resulting Hamiltonian contains direct qubit-qubit interactions, which have a
drastic effect on the ground and excited state properties of such circuits in
the ultrastrong coupling regime. In contrast to a superradiant phase transition
expected from the standard Dicke model, we find an opposite mechanism, which at
very strong interactions completely decouples the photon mode and projects the
qubits into a highly entangled ground state. These findings resolve previous
controversies over the existence of superradiant phases in circuit QED, but
they more generally show that the physics of two- or multi-atom cavity QED
settings can differ significantly from what is commonly assumed.Comment: 11 pages, 8 figure
Digital Quantum Rabi and Dicke Models in Superconducting Circuits
We propose the analog-digital quantum simulation of the quantum Rabi and
Dicke models using circuit quantum electrodynamics (QED). We find that all
physical regimes, in particular those which are impossible to realize in
typical cavity QED setups, can be simulated via unitary decomposition into
digital steps. Furthermore, we show the emergence of the Dirac equation
dynamics from the quantum Rabi model when the mode frequency vanishes. Finally,
we analyze the feasibility of this proposal under realistic superconducting
circuit scenarios.Comment: 5 pages, 3 figures. Published in Scientific Report
On-Chip Photonic Transistor based on the Spike Synchronization in Circuit QED
We consider the single photon transistor in coupled cavity system of
resonators interacting with multilevel superconducting artificial atom
simultaneously. Effective single mode transformation is used for the
diagonalization of the the hamiltonian and impedance matching in terms of the
normal modes. Storage and transmission of the incident field are described by
the interactions between the cavities controlling the atomic transitions of
lowest lying states. Rabi splitting of vacuum induced multiphoton transitions
is considered in input/output relations by the quadrature operators in the
absence of the input field. Second order coherence functions are employed to
investigate the photon blockade and localization-delocalization transitions of
cavity fields in oscillating regime of photon states described by the the
population imbalance. Refection and transmission of cavity output fields are
investigated in the presence of the multilevel transitions. Accumulation and
firing of the reflected and transmitted fields are used to investigate the
synchronization of the bunching spike train of transmitted field and population
imbalance of cavity fields. In the presence of single photon gate field, gain
enhancement is explained for transmitted regime.Comment: 8 pages,10 figure
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