106 research outputs found
Experimental demonstration of quantum state tomography and qubit-qubit interactions for rare-earth-ion based solid state qubits
We report on the implementation of quantum state tomography for an ensemble
of Eu dopant ions in a \YSO crystal. The tomography was applied to a
qubit based on one of the ion's optical transitions. The qubit was manipulated
using optical pulses and measurements were made by observing the optical free
induction in a phase sensitive manner. Fidelities of % for the combined
preparation and measurement process were achieved. Interactions between the
ions due to the change in the ions' permanent electric dipole moment when
excited optically were also measured. In light of these results, the ability to
do multi-qubit quantum computation using this system is discussed
Demonstration of conditional quantum phase shift between ions in a solid
Due to their potential for long coherence times, dopant ions have long been
considered promising candidates for scalable solid state quantum computing.
However, the demonstration of two qubit operation has proven to be problematic,
largely due to the difficulty of addressing closely spaced ions. Here we use
optically active ions and optical frequency addressing to demonstrate a
conditional phase shift between two qubits
Analytic treatment of controlled reversible inhomogeneous broadening quantum memories for light using two-level atoms
It has recently been discovered that the optical analog of a gradient echo, in an optically thick material, could
form the basis of an optical memory that is both completely efficient and noise-free. Here we present analytical
calculations showing that this is the case. There is close analogy between the operation of the memory and an
optical system with two beam splitters. We can use this analogy to calculate efficiencies as a function of optical
depth for a number of quantum memory schemes based on controlled inhomogeneous broadening. In particular,
we show that multiple switching leads to a net 100% retrieval efficiency for the optical gradient echo even
in the optically thin case
Coherent spectroscopy of rare-earth-ion doped whispering-gallery mode resonators
We perform an investigation into the properties of Pr3+:Y2SiO5 whispering
gallery mode resonators as a first step towards achieving the strong coupling
regime of cavity QED with rare-earth-ion doped crystals. Direct measurement of
cavity QED parameters are made using photon echoes, giving good agreement with
theoretical predictions. By comparing the ions at the surface of the resonator
to those in the center it is determined that the physical process of making the
resonator does not negatively affect the properties of the ions. Coupling
between the ions and resonator is analyzed through the observation of optical
bistability and normal-mode splitting.Comment: 8 pages, 9 figure
Photon echo without a free induction decay in a double-Lambda system
We have characterized a novel photon-echo pulse sequence for a
double- type energy level system where the input and rephasing
transitions are different to the applied -pulses. We show that despite
having imperfect -pulses (associated with large coherent emission due to
free induction decay), the noise added is only 0.0190.001 relative to the
shot noise in the spectral mode of the echo. Using this echo pulse sequence in
the `rephased amplified spontaneous emission' (RASE) scheme
\cite{Ledingham2010} will allow for generation of entangled photon pairs that
are in different frequency, temporal, and potentially spatial modes to any
bright driving fields. The coherence and efficiency properties of this sequence
were characterized in a Pr:YSO crystal
Analytic treatment of CRIB Quantum Memories for Light using Two-level Atoms
It has recently been discovered that the optical analogue of a gradient echo
in an optically thick material could form the basis of a optical memory that is
both completely efficient and noise free. Here we present analytical
calculation showing this is the case. There is close analogy between the
operation of the memory and an optical system with two beam splitters. We can
use this analogy to calculate efficiencies as a function of optical depth for a
number of quantum memory schemes based on controlled inhomogeneous broadening.
In particular we show that multiple switching leads to a net 100% retrieval
efficiency for the optical gradient echo even in the optically thin case.Comment: 10 page
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