43 research outputs found
Dynamical Casimir Effect for Gaussian Boson Sampling
We show that the Dynamical Casimir Effect (DCE), realized on two multimode
coplanar waveguide resonators, implements a gaussian boson sampler (GBS). The
appropriate choice of the mirror acceleration that couples both resonators
translates into the desired initial gaussian state and many-boson interference
in a boson sampling network. In particular, we show that the proposed quantum
simulator naturally performs a classically hard task, known as scattershot
boson sampling. Our result unveils an unprecedented computational power of DCE,
and paves the way for using DCE as a resource for quantum simulation.Comment: 5 pages, 2 figures. v2:minor changes, published versio
Spin models and boson sampling
In this work we proof that boson sampling with particles in modes is
equivalent to short-time evolution with excitations in an XY model of
spins. This mapping is efficient whenever the boson bunching probability is
small, and errors can be efficiently postselected. This mapping opens the door
to boson sampling with quantum simulators or general purpose quantum computers,
and highlights the complexity of time-evolution with critical spin models, even
for very short times.Comment: Extended supplementary material; typos fixed in the proof equation
Quantum Emulation of Molecular Force Fields: A Blueprint for a Superconducting Architecture
In this work, we propose a flexible architecture of microwave resonators with
tunable couplings to perform quantum simulations of problems from the field of
molecular chemistry. The architecture builds on the experience of the D-Wave
design, working with nearly harmonic circuits instead of qubits. This
architecture, or modifications of it, can be used to emulate molecular
processes such as vibronic transitions. Furthermore, we discuss several aspects
of these emulations, such as dynamical ranges of the physical parameters,
quenching times necessary for diabaticity, and, finally, the possibility of
implementing anharmonic corrections to the force fields by exploiting certain
nonlinear features of superconducting devices.Comment: 14 pages, 4 figure
Quantum Simulation with a Boson Sampling Circuit
In this work we study a system that consists of matter qubits that
interact through a boson sampling circuit, i.e., an -port interferometer,
embedded in two different architectures. We prove that, under the conditions
required to derive a master equation, the qubits evolve according to effective
bipartite XY spin Hamiltonians, with or without local and collective
dissipation terms. This opens the door to the simulation of any bipartite spin
or hard-core boson models and exploring dissipative phase transitions as the
competition between coherent and incoherent exchange of excitations. We also
show that in the purely dissipative regime this model has a large number of
exact and approximate dark states, whose structure and decay rates can be
estimated analytically. We finally argue that this system may be used for the
adiabatic preparation of boson sampling states encoded in the matter qubits.Comment: 9 pages, 3 figure
Extracting past-future vacuum correlations using circuit QED
We propose a realistic circuit QED experiment to test the extraction of
past-future vacuum entanglement to a pair of superconducting qubits. The qubit
P interacts with the quantum field along an open transmission line for an
interval T_on and then, after a time-lapse T_off, the qubit F starts
interacting for a time T_on in a symmetric fashion. After that, past-future
quantum correlations will have transferred to the qubits, even if the qubits do
not coexist at the same time. We show that this experiment can be realized with
current technology and discuss its utility as a possible implementation of a
quantum memory.Comment: 5 pages, 2 figures. v2: version accepted to Physical Review Letters.
Title changed by editor
The Single-Photon Router
We have embedded an artificial atom, a superconducting "transmon" qubit, in
an open transmission line and investigated the strong scattering of incident
microwave photons ( GHz). When an input coherent state, with an average
photon number is on resonance with the artificial atom, we observe
extinction of up to 90% in the forward propagating field. We use two-tone
spectroscopy to study scattering from excited states and we observe
electromagnetically induced transparency (EIT). We then use EIT to make a
single-photon router, where we can control to what output port an incoming
signal is delivered. The maximum on-off ratio is around 90% with a rise and
fall time on the order of nanoseconds, consistent with theoretical
expectations. The router can easily be extended to have multiple output ports
and it can be viewed as a rudimentary quantum node, an important step towards
building quantum information networks.Comment: 5 pages, 3 figure
Light-matter decoupling and A2 term detection in superconducting circuits
APS March Meeting 2015, San Antonio, Texas, March 2–6, 2015We study the spontaneous emission of a qubit interacting with a one-dimensional waveguide through a realistic minimal-coupling interaction. We show that the diamagnetic term A2 leads to an effective decoupling of a single qubit from the electromagnetic field. This effect is observable at any range of qubit-photon couplings. For this we study a setup consisting of a transmon that is suspended over a transmission line. Assuming a standard model of qubit-line interaction, we prove that the relative strength of the A2 term is controlled with the qubit-line separation and show that, as a consequence, the spontaneous emission rate of the suspended transmon onto the line can increase with such separation, instead of decreasing.Peer Reviewe
Light-matter decoupling and term detection in superconducting circuits
We study the spontaneous emission of a qubit interacting with a
one-dimensional waveguide through a realistic minimal-coupling interaction. We
show that the diamagnetic term leads to an effective decoupling of a
single qubit from the electromagnetic field. This effects is observable at any
range of qubit-photon couplings. For this we study a setup consisting of a
transmon that is suspended over a transmission line. We prove that the relative
strength of the term is controlled with the qubit-line separation and
show that, as a consequence, the spontaneous emission rate of the suspended
transmon onto the line can increase with such separation, instead of
decreasing.Comment: 5 pages,4 figure
Dynamics of superconducting qubits in open transmission lines
Resumen del trabajo presentado al "APS March Meeting" celebrado en Denver, Colorado (US) del 3 al 7 de marzo de 2014.The time and space resolved dynamics of a superconducting qubit with an Ohmic coupling to propagating 1D photons is studied, from weak coupling to the ultrastrong coupling regime (USC). A nonperturbative study based on Matrix Product States (MPS) shows the following results: (i) The ground state of the combined systems contains excitations of both the qubit and the surrounding bosonic field. (ii) An initially excited qubit equilibrates through spontaneous emission to a state, which under certain conditions, is locally close to that ground state, both in the qubit and the field. (iii) The resonances of the combined qubit-photon system match those of the spontaneous emission process and also the predictions of the adiabatic renormalisation. These results set the foundations for future studies and engineering of the interactions between superconducting qubits and propagating photons, as well as the design of photon-photon interactions based on artificial materials built from these qubits.Peer Reviewe