144 research outputs found
Single electron relativistic clock interferometer
Although time is one of the fundamental notions in physics, it does not have
a unique description. In quantum theory time is a parameter ordering the
succession of the probability amplitudes of a quantum system, while according
to relativity theory each system experiences in general a different proper
time, depending on the system's world line, due to time to time dilation. It is
therefore of fundamental interest to test the notion of time in the regime
where both quantum and relativistic effects play a role, for example, when
different amplitudes of a single quantum clock experience different magnitudes
of time dilation. Here we propose a realization of such an experiment with a
single electron in a Penning trap. The clock can be implemented in the
electronic spin precession and its time dilation then depends on the radial
(cyclotron) state of the electron. We show that coherent manipulation and
detection of the electron can be achieved already with present day technology.
A single electron in a Penning trap is a technologically ready platform where
the notion of time can be probed in a hitherto untested regime, where it
requires a relativistic as well as quantum description.Comment: 9 pages, 4 figure
Interfacing microwave qubits and optical photons via spin ensembles
A protocol is discussed which allows one to realize a transducer for single
photons between the optical and the microwave frequency range. The transducer
is a spin ensemble, where the individual emitters possess both an optical and a
magnetic-dipole transition. Reversible frequency conversion is realized by
combining optical photon storage, by means of EIT, with the controlled
switching of the coupling between the magnetic-dipole transition and a
superconducting qubit, which is realized by means of a microwave cavity. The
efficiency is quantified by the global fidelity for transferring coherently a
qubit excitation between a single optical photon and the superconducting qubit.
We test various strategies and show that the total efficiency is essentially
limited by the optical quantum memory: It can exceed 80% for ensembles of NV
centers and approaches 99% for cold atomic ensembles, assuming state-of-the-art
experimental parameters. This protocol allows one to bridge the gap between the
optical and the microwave regime so to efficiently combine superconducting and
optical components in quantum networks
Multi-photon spectroscopy of a hybrid quantum system
We report on experimental multi-photon spectroscopy of a hybrid quantum
system consisting of a superconducting phase qubit coherently coupled to an
intrinsic two-level defect. We directly probe hybridized states of the combined
qubit-defect system in the strongly interacting regime, where both the
qubit-defect coupling and the driving cannot be considered as weak
perturbations. This regime is described by a theoretical model which
incorporates anharmonic corrections, multi-photon processes and decoherence. We
present a detailed comparison between experiment and theory and find excellent
agreement over a wide range of parameters.Comment: 6 pages, 6 figure
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
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