3,421 research outputs found
A thermodynamical model for non-extremal black p-brane
We show that the correct entropy, temperature (and absorption probability) of
non-extremal black p-brane can be reproduced by a certain thermodynamical model
when maximizing its entropy. We show that the form of the model is related to
the geometrical similarity of non-extremal and near extremal black p-brane at
near horizon region, and argue about the appropriateness of the model.Comment: Almost the same version as the paper appeared in Physical Review
The Electric Double Layer Structure Around Charged Spherical Interfaces
We derive a formally simple approximate analytical solution to the
Poisson-Boltzmann equation for the spherical system via a geometric mapping.
Its regime of applicability in the parameter space of the spherical radius and
the surface potential is determined, and its superiority over the linearized
solution is demonstrated.Comment: 7 pages, 5 figure
Multi-mode storage and retrieval of microwave fields in a spin ensemble
A quantum memory at microwave frequencies, able to store the state of
multiple superconducting qubits for long times, is a key element for quantum
information processing. Electronic and nuclear spins are natural candidates for
the storage medium as their coherence time can be well above one second.
Benefiting from these long coherence times requires to apply the refocusing
techniques used in magnetic resonance, a major challenge in the context of
hybrid quantum circuits. Here we report the first implementation of such a
scheme, using ensembles of nitrogen-vacancy (NV) centres in diamond coupled to
a superconducting resonator, in a setup compatible with superconducting qubit
technology. We implement the active reset of the NV spins into their ground
state by optical pumping and their refocusing by Hahn echo sequences. This
enables the storage of multiple microwave pulses at the picoWatt level and
their retrieval after up to s, a three orders of magnitude improvement
compared to previous experiments.Comment: 8 pages, 5 figures + Supplementary information (text and 6 figures
Electron spin resonance detected by a superconducting qubit
A new method for detecting the magnetic resonance of electronic spins at low
temperature is demonstrated. It consists in measuring the signal emitted by the
spins with a superconducting qubit that acts as a single-microwave-photon
detector, resulting in an enhanced sensitivity. We implement this new type of
electron-spin resonance spectroscopy using a hybrid quantum circuit in which a
transmon qubit is coupled to a spin ensemble consisting of NV centers in
diamond. With this setup we measure the NV center absorption spectrum at 30mK
at an excitation level of \thicksim15\,\mu_{B} out of an ensemble of 10^{11}
spins.Comment: 6 pages, 4 figures, submitted to PR
- …