37 research outputs found
Extending Phenomenological Crystal-Field Methods to C1 Point-Group Symmetry: Characterization of the Optically Excited Hyperfine Structure of Er1673+:Y2SiO5
We show that crystal-field calculations for C1 point-group symmetry are possible, and that such
calculations can be performed with sufficient accuracy to have substantial utility for rare-earth based
quantum information applications. In particular, we perform crystal-field fitting for a C1-symmetry site in
167Er3þ∶Y2SiO5. The calculation simultaneously includes site-selective spectroscopic data up to
20 000 cm−1, rotational Zeeman data, and ground- and excited-state hyperfine structure determined from
high-resolution Raman-heterodyne spectroscopy on the 1.5 μm telecom transition. We achieve an
agreement of better than 50 MHz for assigned hyperfine transitions. The success of this analysis opens
the possibility of systematically evaluating the coherence properties, as well as transition energies and
intensities, of any rare-earth ion doped into Y2SiO5
A comprehensive understanding of ground and optically-excited hyperfine structure of ¹⁶⁷Er³+:Y2SiO5
Using high-performance computing techniques and targeted experimental
investigation we have developed a predictive crystal-field model of the complex
hyperfine structure of ¹⁶⁷Er³+:Y2SiO5 We simultaneously match
site-selective spectroscopic data up to 20,000 cm-¹, rotational Zeeman
data, and ground- and excited-state hyperfine structure determined from
high-resolution Raman-heterodyne spectroscopy on the 1.5 μm telecom
transition. We achieve agreement of better than 50 MHz for assigned hyperfine
transitions. The successful analysis of the complex hyperfine patterns opens
the possibility of systematically searching this whole class of materials for
the ZEFOZ transitions that have proved so useful in quantum information
applications
Quantum Storage of Photonic Entanglement in a Crystal
Entanglement is the fundamental characteristic of quantum physics. Large
experimental efforts are devoted to harness entanglement between various
physical systems. In particular, entanglement between light and material
systems is interesting due to their prospective roles as "flying" and
stationary qubits in future quantum information technologies, such as quantum
repeaters and quantum networks. Here we report the first demonstration of
entanglement between a photon at telecommunication wavelength and a single
collective atomic excitation stored in a crystal. One photon from an
energy-time entangled pair is mapped onto a crystal and then released into a
well-defined spatial mode after a predetermined storage time. The other photon
is at telecommunication wavelength and is sent directly through a 50 m fiber
link to an analyzer. Successful transfer of entanglement to the crystal and
back is proven by a violation of the Clauser-Horne-Shimony-Holt (CHSH)
inequality by almost three standard deviations (S=2.64+/-0.23). These results
represent an important step towards quantum communication technologies based on
solid-state devices. In particular, our resources pave the way for building
efficient multiplexed quantum repeaters for long-distance quantum networks.Comment: 5 pages, 3 figures + supplementary information; fixed typo in ref.
[36
A solid state light-matter interface at the single photon level
Coherent and reversible mapping of quantum information between light and
matter is an important experimental challenge in quantum information science.
In particular, it is a decisive milestone for the implementation of quantum
networks and quantum repeaters. So far, quantum interfaces between light and
atoms have been demonstrated with atomic gases, and with single trapped atoms
in cavities. Here we demonstrate the coherent and reversible mapping of a light
field with less than one photon per pulse onto an ensemble of 10 millions atoms
naturally trapped in a solid. This is achieved by coherently absorbing the
light field in a suitably prepared solid state atomic medium. The state of the
light is mapped onto collective atomic excitations on an optical transition and
stored for a pre-programmed time up of to 1 mu s before being released in a
well defined spatio-temporal mode as a result of a collective interference. The
coherence of the process is verified by performing an interference experiment
with two stored weak pulses with a variable phase relation. Visibilities of
more than 95% are obtained, which demonstrates the high coherence of the
mapping process at the single photon level. In addition, we show experimentally
that our interface allows one to store and retrieve light fields in multiple
temporal modes. Our results represent the first observation of collective
enhancement at the single photon level in a solid and open the way to multimode
solid state quantum memories as a promising alternative to atomic gases.Comment: 5 pages, 5 figures, version submitted on June 27 200
Towards high-speed optical quantum memories
Quantum memories, capable of controllably storing and releasing a photon, are
a crucial component for quantum computers and quantum communications. So far,
quantum memories have operated with bandwidths that limit data rates to MHz.
Here we report the coherent storage and retrieval of sub-nanosecond low
intensity light pulses with spectral bandwidths exceeding 1 GHz in cesium
vapor. The novel memory interaction takes place via a far off-resonant
two-photon transition in which the memory bandwidth is dynamically generated by
a strong control field. This allows for an increase in data rates by a factor
of almost 1000 compared to existing quantum memories. The memory works with a
total efficiency of 15% and its coherence is demonstrated by directly
interfering the stored and retrieved pulses. Coherence times in hot atomic
vapors are on the order of microsecond - the expected storage time limit for
this memory.Comment: 13 pages, 5 figure
Heralded quantum entanglement between two crystals
Quantum networks require the crucial ability to entangle quantum nodes. A
prominent example is the quantum repeater which allows overcoming the distance
barrier of direct transmission of single photons, provided remote quantum
memories can be entangled in a heralded fashion. Here we report the observation
of heralded entanglement between two ensembles of rare-earth-ions doped into
separate crystals. A heralded single photon is sent through a 50/50
beamsplitter, creating a single-photon entangled state delocalized between two
spatial modes. The quantum state of each mode is subsequently mapped onto a
crystal, leading to an entangled state consisting of a single collective
excitation delocalized between two crystals. This entanglement is revealed by
mapping it back to optical modes and by estimating the concurrence of the
retrieved light state. Our results highlight the potential of rare-earth-ions
doped crystals for entangled quantum nodes and bring quantum networks based on
solid-state resources one step closer.Comment: 10 pages, 5 figure
Control of microwave signals using circuit nano-electromechanics
Waveguide resonators are crucial elements in sensitive astrophysical
detectors [1] and circuit quantum electrodynamics (cQED) [2]. Coupled to
artificial atoms in the form of superconducting qubits [3, 4], they now provide
a technologically promising and scalable platform for quantum information
processing tasks [2, 5-8]. Coupling these circuits, in situ, to other quantum
systems, such as molecules [9, 10], spin ensembles [11, 12], quantum dots [13]
or mechanical oscillators [14, 15] has been explored to realize hybrid systems
with extended functionality. Here, we couple a superconducting coplanar
waveguide resonator to a nano-coshmechanical oscillator, and demonstrate
all-microwave field controlled slowing, advancing and switching of microwave
signals. This is enabled by utilizing electromechanically induced transparency
[16-18], an effect analogous to electromagnetically induced transparency (EIT)
in atomic physics [19]. The exquisite temporal control gained over this
phenomenon provides a route towards realizing advanced protocols for storage of
both classical and quantum microwave signals [20-22], extending the toolbox of
control techniques of the microwave field.Comment: 9 figure
A millisecond quantum memory for scalable quantum networks
Scalable quantum information processing critically depends on the capability
of storage of a quantum state. In particular, a long-lived storable and
retrievable quantum memory for single excitations is of crucial importance to
the atomic-ensemble-based long-distance quantum communication. Although atomic
memories for classical lights and continuous variables have been demonstrated
with milliseconds storage time, there is no equal advance in the development of
quantum memory for single excitations, where only around 10 s storage time
was achieved. Here we report our experimental investigations on extending the
storage time of quantum memory for single excitations. We isolate and identify
distinct mechanisms for the decoherence of spin wave (SW) in atomic ensemble
quantum memories. By exploiting the magnetic field insensitive state, ``clock
state", and generating a long-wavelength SW to suppress the dephasing, we
succeed in extending the storage time of the quantum memory to 1 ms. Our result
represents a substantial progress towards long-distance quantum communication
and enables a realistic avenue for large-scale quantum information processing.Comment: 11pages, 4 figures, submitted for publicatio
A Raman heterodyne determination of the magnetic anisotropy for the ground and optically excited states of YSiO doped with Sm
We present the full magnetic g tensors of the 6H5/2Z1 and 4G5/2A1 electronic states for both
crystallographic sites in Sm3+:Y2SiO5, deduced through the use of Raman heterodyne spectroscopy
performed along 9 different crystallographic directions. The maximum principle g values were determined to be 0.447 (site 1) and 0.523 (site 2) for the ground state and 2.490 (site 1) and 3.319 (site
2) for the excited state. The determination of these g tensors provide essential spin Hamiltonian
parameters that can be utilized in future magnetic and hyperfine studies of Sm3+:Y2SiO5, with
applications in quantum information storage and communication devices
Transferability of crystal-field parameters for rare-earth ions in YSiO tested by Zeeman spectroscopy
Zeeman spectroscopy is used to demonstrate that phenomenological
crystal-field parameters determined for the two point-group sites in
Er:YSiO may be transferred to other ions. The two
crystallographic six- and seven-coordinate substitutional sites may be
distinguished by comparing the spectra with crystal-field calculations