61 research outputs found
Coherent Storage of Temporally Multimode Light Using a Spin-Wave Atomic Frequency Comb Memory
We report on coherent and multi-temporal mode storage of light using the full
atomic frequency comb memory scheme. The scheme involves the transfer of
optical atomic excitations in Pr3+:Y2SiO5 to spin-waves in the hyperfine levels
using strong single-frequency transfer pulses. Using this scheme, a total of 5
temporal modes are stored and recalled on-demand from the memory. The coherence
of the storage and retrieval is characterized using a time-bin interference
measurement resulting in visibilities higher than 80%, independent of the
storage time. This coherent and multimode spin-wave memory is promising as a
quantum memory for light.Comment: 17 pages, 5 figure
A solid state spin-wave quantum memory for time-bin qubits
We demonstrate the first solid-state spin-wave optical quantum memory with
on-demand read-out. Using the full atomic frequency comb scheme in a \PrYSO
crystal, we store weak coherent pulses at the single-photon level with a signal
to noise ratio . Narrow-band spectral filtering based on spectral hole
burning in a second \PrYSO crystal is used to filter out the excess noise
created by control pulses to reach an unconditional noise level of photons per pulse. We also report spin-wave storage of
photonic time-bin qubits with conditional fidelities higher than a measure and
prepare strategy, demonstrating that the spin-wave memory operates in the
quantum regime. This makes our device the first demonstration of a quantum
memory for time-bin qubits, with on demand read-out of the stored quantum
information. These results represent an important step for the use of
solid-state quantum memories in scalable quantum networks.Comment: 10 pages, 10 figure
Storage of up-converted telecom photons in a doped crystal
We report on an experiment that demonstrates the frequency up-conversion of
telecommunication wavelength single-photon-level pulses to be resonant with a
: crystal. We convert
the telecom photons at to using a
periodically-poled potassium titanyl phosphate nonlinear waveguide. The maximum
device efficiency (which includes all optical loss) is inferred to be
(internal efficiency
) with a signal to noise ratio exceeding 1 for
single-photon-level pulses with durations of up to 560ns. The converted
light is then stored in the crystal using the atomic frequency comb scheme with
storage and retrieval efficiencies exceeding for
predetermined storage times of up to . The retrieved light is
time delayed from the noisy conversion process allowing us to measure a signal
to noise ratio exceeding 100 with telecom single-photon-level inputs. These
results represent the first demonstration of single-photon-level optical
storage interfaced with frequency up-conversion
Frequency-Bin Entanglement of Ultra-Narrow Band Non-Degenerate Photon Pairs
We demonstrate frequency-bin entanglement between ultra-narrowband photons
generated by cavity enhanced spontaneous parametric down conversion. Our source
generates photon pairs in widely non-degenerate discrete frequency modes, with
one photon resonant with a quantum memory material based on praseodymium doped
crystals and the other photon at telecom wavelengths. Correlations between the
frequency modes are analyzed using phase modulators and narrowband filters
before detection. We show high-visibility two photon interference between the
frequency modes, allowing us to infer a coherent superposition of the modes. We
develop a model describing the state that we create and use it to estimate
optimal measurements to achieve a violation of the Clauser-Horne (CH) Bell
inequality under realistic assumptions. With these settings we perform a Bell
test and show a significant violation of the CH inequality, thus proving the
entanglement of the photons. Finally we demonstrate the compatibility with a
quantum memory material by using a spectral hole in the praseodymium (Pr) doped
crystal as spectral filter for measuring high-visibility two-photon
interference. This demonstrates the feasibility of combining frequency-bin
entangled photon pairs with Pr-based solid state quantum memories.Comment: 15 pages, 6 figure
A spectral hole memory for light at the single photon level
We demonstrate a solid state spin-wave optical memory based on stopped light
in a spectral hole. A long lived narrow spectral hole is created by optical
pumping in the inhomogeneous absorption profile of a Pr:YSiO
crystal. Optical pulses sent through the spectral hole experience a strong
reduction of their group velocity and are spatially compressed in the crystal.
A short Raman pulse transfers the optical excitation to the spin state before
the light pulse exits the crystal, effectively stopping the light. After a
controllable delay, a second Raman pulse is sent, which leads to the emission
of the stored photons. We reach storage and retrieval efficiencies for bright
pulses of up to in a -long crystal. We also show that
our device works at the single photon level by storing and retrieving
-long weak coherent pulses with efficiencies up to ,
demonstrating the most efficient spin-wave solid state optical memory at the
single-photon level so far. We reach an unconditional noise level of
photons per pulse in a detection window of
leading to a signal-to-noise ratio of for an
average input photon number of 1, making our device promising for long-lived
storage of non-classical light.Comment: 5 pages, 4 figure
High resolution spectroscopy to investigate impurities in YAB single crystals
The work explores the feasibility of high resolution (as fine as 0.02 cm-1) Fourier transform spectroscopy applied at 9 K in the 500-25000 cm-1 range to detect traces of unwanted impurities, mainly rare earths (RE3+) in crystals: the system chosen is YAl3(BO3)4 (YAB). Weak traces of RE3+ (Nd, Dy, Er, Tm, Yb), but also of Cr3+ and OH-, were successfully monitored by comparing the spectra of YAB samples under examination with those intentionally doped with a given ion. The analysis performed on a variety of samples shows how Cr3+, Nd3+, and Yb3+ are the most frequent unwanted dopants and can provide suggestions to the crystal growers about the performances of different crystal growth lines. According to a preliminary evaluation, the Er3+ traces detection limit is as low as 1-2x10-4 mol% in 1 cm thick samples. The advantages of the method, which is sample non-destructive, are discussed in comparison with those currently applied
Entanglement between a telecom photon and an on-demand multimode solid-state quantum memory
Entanglement between photons at telecommunication wavelengths and long-lived
quantum memories is one of the fundamental requirements of long-distance
quantum communication. Quantum memories featuring on-demand read-out and
multimode operation are additional precious assets that will benefit the
communication rate. In this work we report the first demonstration of
entanglement between a telecom photon and a collective spin excitation in a
multimode solid-state quantum memory. Photon pairs are generated through widely
non-degenerate parametric down-conversion, featuring energy-time entanglement
between the telecom-wavelength idler and a visible signal photon. The latter is
stored in a Pr:YSiO crystal as a spin wave using the full Atomic
Frequency Comb scheme. We then recall the stored signal photon and analyze the
entanglement using the Franson scheme. We measure conditional fidelities of
for excited-state storage, enough to violate a CHSH inequality, and
for spin-wave storage. Taking advantage of the on-demand read-out
from the spin state, we extend the entanglement storage in the quantum memory
for up to 47.7~s, which could allow for the distribution of entanglement
between quantum nodes separated by distances of up to 10 km
Quantum storage of heralded single photons in a praseodymium-doped crystal
We report on experiments demonstrating the reversible mapping of heralded single photons to long-lived collective optical atomic excitations stored in a Pr3+:Y2SiO5 crystal. A cavity-enhanced spontaneous down-conversion source is employed to produce widely nondegenerate narrow-band (≈2 MHz) photon pairs. The idler photons, whose frequency is compatible with telecommunication optical fibers, are used to herald the creation of the signal photons, compatible with the Pr3þ transition. The signal photons are stored and retrieved using the atomic frequency comb protocol. We demonstrate storage times up to 4.5 μs while preserving nonclassical correlations between the heralding and the retrieved photon. This is more than 20 times longer than in previous realizations in solid state devices, and implemented in a system ideally suited for the extension to spin-wave storage
Photonic quantum state transfer between a cold atomic gas and a crystal
Interfacing fundamentally different quantum systems is key to build future
hybrid quantum networks. Such heterogeneous networks offer superior
capabilities compared to their homogeneous counterparts as they merge
individual advantages of disparate quantum nodes in a single network
architecture. However, only very few investigations on optical
hybrid-interconnections have been carried out due to the high fundamental and
technological challenges, which involve e.g. wavelength and bandwidth matching
of the interfacing photons. Here we report the first optical quantum
interconnection between two disparate matter quantum systems with photon
storage capabilities. We show that a quantum state can be faithfully
transferred between a cold atomic ensemble and a rare-earth doped crystal via a
single photon at telecommunication wavelength, using cascaded quantum frequency
conversion. We first demonstrate that quantum correlations between a photon and
a single collective spin excitation in the cold atomic ensemble can be
transferred onto the solid-state system. We also show that single-photon
time-bin qubits generated in the cold atomic ensemble can be converted, stored
and retrieved from the crystal with a conditional qubit fidelity of more than
. Our results open prospects to optically connect quantum nodes with
different capabilities and represent an important step towards the realization
of large-scale hybrid quantum networks
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