83 research outputs found
Measuring the temperature dependence of individual two-level systems by direct coherent control
We demonstrate a new method to directly manipulate the state of individual
two-level systems (TLS) in phase qubits. It allows one to characterize the
coherence properties of TLS using standard microwave pulse sequences, while the
qubit is used only for state readout. We apply this method to measure the
temperature dependence of TLS coherence for the first time. The energy
relaxation time is found to decrease quadratically with temperature for
the two TLS studied in this work, while their dephasing time measured in Ramsey
and spin-echo experiments is found to be limited at all temperatures.Comment: 4 pages, 5 figure
Entangling microscopic defects via a macroscopic quantum shuttle
In the microscopic world, multipartite entanglement has been achieved with
various types of nanometer sized two-level systems such as trapped ions, atoms
and photons. On the macroscopic scale ranging from micrometers to millimeters,
recent experiments have demonstrated bipartite and tripartite entanglement for
electronic quantum circuits with superconducting Josephson junctions. It
remains challenging to bridge these largely different length scales by
constructing hybrid quantum systems. Doing this may allow for manipulating the
entanglement of individual microscopic objects separated by macroscopically
large distances in a quantum circuit. Here we report on the experimental
demonstration of induced coherent interaction between two intrinsic two-level
states (TLSs) formed by atomic-scale defects in a solid via a superconducting
phase qubit. The tunable superconducting circuit serves as a shuttle
communicating quantum information between the two microscopic TLSs. We present
a detailed comparison between experiment and theory and find excellent
agreement over a wide range of parameters. We then use the theoretical model to
study the creation and movement of entanglement between the three components of
the quantum system.Comment: 11 pages, 5 figure
Optical vector network analysis of ultra-narrow transitions in Er:LiYF
We present optical vector network analysis (OVNA) of an isotopically purified
Er:LiYF crystal. The OVNA method is based on generation
and detection of modulated optical sideband by using a radio-frequency vector
network analyzer. This technique is widely used in the field of microwave
photonics for the characterization of optical responses of optical devices such
as filters and high-Q resonators. However, dense solid-state atomic ensembles
induce a large phase shift on one of the optical sidebands which results in the
appearance of extra features on the measured transmission response. We present
a simple theoretical model which accurately describes the observed spectra and
helps to reconstruct the absorption profile of a solid-state atomic ensemble as
well as corresponding change of the refractive index in the vicinity of atomic
resonances.Comment: 4 pages, 5 figure
Quantitative evaluation of defect-models in superconducting phase qubits
We use high-precision spectroscopy and detailed theoretical modelling to
determine the form of the coupling between a superconducting phase qubit and a
two-level defect. Fitting the experimental data with our theoretical model
allows us to determine all relevant system parameters. A strong qubit-defect
coupling is observed, with a nearly vanishing longitudinal component. Using
these estimates, we quantitatively compare several existing theoretical models
for the microscopic origin of two-level defects.Comment: 3 pages, 2 figures. Supplementary material, lclimits_supp.pd
Strong extinction of a laser beam by a single molecule
We present an experiment where a single molecule strongly affects the
amplitude and phase of a laser field emerging from a subwavelength aperture. We
achieve a visibility of -6% in direct and +10% in cross-polarized detection
schemes. Our analysis shows that a close to full extinction should be possible
using near-field excitation.Comment: 5 pages, 4 figures, submitted to PR
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