79 research outputs found
Two-resonator circuit QED: Dissipative Theory
We present a theoretical treatment for the dissipative two-resonator circuit
quantum electrodynamics setup referred to as quantum switch. There, switchable
coupling between two superconducting resonators is mediated by a
superconducting qubit operating in the dispersive regime, where the qubit
transition frequency is far detuned from those of the resonators. We derive an
effective Hamiltonian for the quantum switch beyond the rotating wave
approximation and study the dissipative dynamics within a Bloch-Redfield
quantum master equation approach. We derive analytically how the qubit affects
the quantum switch even if the qubit has no dynamics, and we estimate the
strength of this influence. The analytical results are corroborated by
numerical calculations, where coherent oscillations between the resonators, the
decay of coherent and Fock states, and the decay of resonator-resonator
entanglement are studied. Finally, we suggest an experimental protocol for
extracting the damping constants of qubit and resonators by measuring the
quadratures of the resonator fields.Comment: 17 pages, 9 figure
Tunable coupling engineering between superconducting resonators: from sidebands to effective gauge fields
In this work we show that a tunable coupling between microwave resonators can
be engineered by means of simple Josephson junctions circuits, such as dc- and
rf-SQUIDs. We show that by controlling the time dependence of the coupling it
is possible to switch on and off and modulate the cross-talk, boost the
interaction towards the ultrastrong regime, as well as to engineer red and blue
sideband couplings, nonlinear photon hopping and classical gauge fields. We
discuss how these dynamically tunable superconducting circuits enable key
applications in the fields of all optical quantum computing, continuous
variable quantum information and quantum simulation - all within the reach of
state of the art in circuit-QED experiments.Comment: 11 pages, 4 figure
Mechanical frequency control in inductively coupled electromechanical systems
Nano-electromechanical systems implement the opto-mechanical interaction
combining electromagnetic circuits and mechanical elements. We investigate an
inductively coupled nano-electromechanical system, where a superconducting
quantum interference device (SQUID) realizes the coupling. We show that the
resonance frequency of the mechanically compliant string embedded into the
SQUID loop can be controlled in two different ways: (i) the bias magnetic flux
applied perpendicular to the SQUID loop, (ii) the magnitude of the in-plane
bias magnetic field contributing to the nano-electromechanical coupling. These
findings are quantitatively explained by the inductive interaction contributing
to the effective spring constant of the mechanical resonator. In addition, we
observe a residual field dependent shift of the mechanical resonance frequency,
which we attribute to the finite flux pinning of vortices trapped in the
magnetic field biased nanostring.Comment: 5 pages, 3 figure
Tackling tumour cell heterogeneity at the super-resolution level in human colorectal cancer tissue
Tumour cell heterogeneity, and its early individual diagnosis, is one of the most fundamental problems in cancer diagnosis and therapy. Single molecule localisation microscopy (SMLM) resolves subcellular features but has been limited to cultured cell lines only. Since nuclear chromatin architecture and microRNAs are critical in metastasis, we introduce a first-in-field approach for quantitative SMLM-analysis of chromatin nanostructure in individual cells in resected, routine-pathology colorectal carcinoma (CRC) patient tissue sections. Chromatin density profiles proved to differ for cells in normal and carcinoma colorectal tissues. In tumour sections, nuclear size and chromatin compaction percentages were significantly different in carcinoma versus normal epithelial and other cells of colorectal tissue. SMLM analysis in nuclei from normal colorectal tissue revealed abrupt changes in chromatin density profiles at the nanoscale, features not detected by conventional widefield microscopy. SMLM for microRNAs relevant for metastasis was achieved in colorectal cancer tissue at the nuclear level. Super-resolution microscopy with quantitative image evaluation algorithms provide powerful tools to analyse chromatin nanostructure and microRNAs of individual cells from normal and tumour tissue at the nanoscale. Our new perspectives improve the differential diagnosis of normal and (metastatically relevant) tumour cells at the single-cell level within the heterogeneity of primary tumours of patients
High cooperativity in coupled microwave resonator ferrimagnetic insulator hybrids
We report the observation of strong coupling between the exchange-coupled
spins in gallium-doped yttrium iron garnet and a superconducting coplanar
microwave resonator made from Nb. The measured coupling rate of 450 MHz is
proportional to the square-root of the number of exchange-coupled spins and
well exceeds the loss rate of 50 MHz of the spin system. This demonstrates that
exchange coupled systems are suitable for cavity quantum electrodynamics
experiments, while allowing high integration densities due to their
extraordinary high spin densities. Our results furthermore show, that
experiments with multiple exchange-coupled spin systems interacting via a
single resonator are within reach.Comment: 5 pages, 3 figure
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