60 research outputs found
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
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
Technique for frequency selective, sub-diffraction limited imaging of rare-earth ions in bulk crystals
We propose and demonstrate the principle of a sub-diffraction-limited optical imaging technique for rare-earth ion crystals that preserves the ions’ homogeneous line width. Our method uses a combination of applied electric field gradients and optical pumping to create a resonant nanoscopic volume within an otherwise non-resonant macroscopic crystal. We present the concept of the Stark activation technique and perform a demonstration in Pr³⁺: Y₂SiO₅ in which we create a 10 μm-thick absorption feature in a 1 mm thick crystal. By modeling the system we show that it is possible to increase the resolution of the technique to the 5 nm range for single Pr³⁺ ions. We also discuss the physical properties that will fundamentally limit the resolution of Stark activation. Because the proposed technique simultaneously achieves high spatial and high spectral resolution it is an enabling protocol to realize technology based on single rare-earth ions and harness short-range interactions in ensembles.This work was supported by the Australian Research Council Center
of Excellence for Quantum Computation and Communication
Technology (CE110001027). M.J.S. was supported by an Australian
Research Council Future Fellowship (FT110100919)
The observation of photon echoes from evanescently coupled rare-earth ions in a planar waveguide
We report the measurement of the inhomogeneous linewidth, homogeneous
linewidth and spin state lifetime of Pr3+ ions in a novel waveguide
architecture. The TeO2 slab waveguide deposited on a bulk Pr3+:Y2SiO5 crystal
allows the 3H4 - 1D2 transition of Pr3+ ions to be probed by the optical
evanescent field that extends into the substrate. The 2 GHz inhomogeneous
linewidth, the optical coherence time of 70 +- 5 us, and the spin state
lifetime of 9.8 +- 0.3 s indicate that the properties of ions interacting with
the waveguide mode are consistent with those of bulk ions. This result
establishes the foundation for large, integrated and high performance
rare-earth-ion quantum systems based on a waveguide platform.Comment: 5 pages, 5 figure
Non-classical photon streams using rephased amplified spontaneous emission
We present a fully quantum mechanical treatment of optically rephased photon
echoes. These echoes exhibit noise due to amplified spontaneous emission,
however this noise can be seen as a consequence of the entanglement between the
atoms and the output light. With a rephasing pulse one can get an "echo" of the
amplified spontaneous emission, leading to light with nonclassical correlations
at points separated in time, which is of interest in the context of building
wide bandwidth quantum repeaters. We also suggest a wideband version of DLCZ
protocol based on the same ideas.Comment: 5 pages, 4 figures. Added section
Single photon production by rephased amplified spontaneous emission
The production of single photons using rephased amplified spontaneous
emission is examined. This process produces single photons on demand with high
efficiency by detecting the spontaneous emission from an atomic ensemble, then
applying a population-inverting pulse to rephase the ensemble and produce a
photon echo of the spontaneous emission events. The theoretical limits on the
efficiency of the production are determined for several variants of the scheme.
For an ensemble of uniform optical density, generating the initial spontaneous
emission and its echo using transitions of different strengths is shown to
produce single photons at 70% efficiency, limited by reabsorption. Tailoring
the spatial and spectral density of the atomic ensemble is then shown to
prevent reabsorption of the rephased photon, resulting in emission efficiency
near unity
Optical addressing of an individual erbium ion in silicon
The detection of electron spins associated with single defects in solids is a
critical operation for a range of quantum information and measurement
applications currently under development. To date, it has only been
accomplished for two centres in crystalline solids: phosphorus in silicon using
electrical readout based on a single electron transistor (SET) and
nitrogen-vacancy centres in diamond using optical readout. A spin readout
fidelity of about 90% has been demonstrated with both electrical readout and
optical readout, however, the thermal limitations of the electrical readout and
the poor photon collection efficiency of the optical readout hinder achieving
the high fidelity required for quantum information applications. Here we
demonstrate a hybrid approach using optical excitation to change the charge
state of the defect centre in a silicon-based SET, conditional on its spin
state, and then detecting this change electrically. The optical frequency
addressing in high spectral resolution conquers the thermal broadening
limitation of the previous electrical readout and charge sensing avoids the
difficulties of efficient photon collection. This is done with erbium in
silicon and has the potential to enable new architectures for quantum
information processing devices and to dramatically increase the range of defect
centres that can be exploited. Further, the efficient electrical detection of
the optical excitation of single sites in silicon is a major step in developing
an interconnect between silicon and optical based quantum computing
technologies.Comment: Corrected the third affiliation. Corrected one cross-reference of
"Fig. 3b" to "Fig. 3c". Corrected the caption of Fig. 3a by changing (+-)1 to
Optimising the Efficiency of a Quantum Memory based on Rephased Amplified Spontaneous Emission
We studied the recall efficiency as a function of optical depth of rephased
amplified spontaneous emission (RASE), a protocol for generating entangled
light. The experiments were performed on the
transition in the rare-earth doped crystal
Pr:YSiO, using a four-level echo sequence between four
hyperfine levels to rephase the emission. Rephased emission was observed for
optical depths in the range of = 0.8 to 2.0 with a maximum rephasing
efficiency of 14 % observed while incorporating spin storage. This efficiency
is a significant improvement over the previously reported non-classical result
but is well short of the predicted efficiency. We discuss the possible
mechanisms limiting the protocol's performance, and suggest ways to overcome
these limits.Comment: 5 pages, 5 figure
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