1,909 research outputs found
Long-lived quantum memory with nuclear atomic spins
We propose to store non-classical states of light into the macroscopic
collective nuclear spin ( atoms) of a He vapor, using
metastability exchange collisions. These collisions, commonly used to transfer
orientation from the metastable state to the ground state state of
He, can also transfer quantum correlations. This gives a possible
experimental scheme to map a squeezed vacuum field state onto a nuclear spin
state with very long storage times (hours).Comment: 4 page
Towards a large-scale quantum simulator on diamond surface at room temperature
Strongly-correlated quantum many-body systems exhibits a variety of exotic
phases with long-range quantum correlations, such as spin liquids and
supersolids. Despite the rapid increase in computational power of modern
computers, the numerical simulation of these complex systems becomes
intractable even for a few dozens of particles. Feynman's idea of quantum
simulators offers an innovative way to bypass this computational barrier.
However, the proposed realizations of such devices either require very low
temperatures (ultracold gases in optical lattices, trapped ions,
superconducting devices) and considerable technological effort, or are
extremely hard to scale in practice (NMR, linear optics). In this work, we
propose a new architecture for a scalable quantum simulator that can operate at
room temperature. It consists of strongly-interacting nuclear spins attached to
the diamond surface by its direct chemical treatment, or by means of a
functionalized graphene sheet. The initialization, control and read-out of this
quantum simulator can be accomplished with nitrogen-vacancy centers implanted
in diamond. The system can be engineered to simulate a wide variety of
interesting strongly-correlated models with long-range dipole-dipole
interactions. Due to the superior coherence time of nuclear spins and
nitrogen-vacancy centers in diamond, our proposal offers new opportunities
towards large-scale quantum simulation at room temperatures
Atomic-like spin noise in solid-state demonstrated with manganese in cadmium telluride
Spin noise spectroscopy is an optical technique which can probe spin
resonances non-perturbatively. First applied to atomic vapours, it revealed
detailed information about nuclear magnetism and the hyperfine interaction. In
solids, this approach has been limited to carriers in semiconductor
heterostructures. Here we show that atomic-like spin fluctuations of Mn ions
diluted in CdT e (bulk and quantum wells) can be detected through the Kerr
rotation associated to excitonic transitions. Zeeman transitions within and
between hyperfine multiplets are clearly observed in zero and small magnetic
fields and reveal the local symmetry because of crystal field and strain. The
linewidths of these resonances are close to the dipolar limit. The sensitivity
is high enough to open the way towards the detection of a few spins in systems
where the decoherence due to nuclear spins can be suppressed by isotopic
enrichment, and towards spin resonance microscopy with important applications
in biology and materials science
Measurement-induced nonlocal entanglement in a hot, strongly-interacting atomic system
Quantum technologies use entanglement to outperform classical technologies,
and often employ strong cooling and isolation to protect entangled entities
from decoherence by random interactions. Here we show that the opposite
strategy - promoting random interactions - can help generate and preserve
entanglement. We use optical quantum non-demolition measurement to produce
entanglement in a hot alkali vapor, in a regime dominated by random
spin-exchange collisions. We use Bayesian statistics and spin-squeezing
inequalities to show that at least of the participating atoms enter into singlet-type entangled states,
which persist for tens of spin-thermalization times and span thousands of times
the nearest-neighbor distance. The results show that high temperatures and
strong random interactions need not destroy many-body quantum coherence, that
collective measurement can produce very complex entangled states, and that the
hot, strongly-interacting media now in use for extreme atomic sensing are well
suited for sensing beyond the standard quantum limit.Comment: 10 pages, 10 figure
Locking Local Oscillator Phase to the Atomic Phase via Weak Measurement
We propose a new method to reduce the frequency noise of a Local Oscillator
(LO) to the level of white phase noise by maintaining (not destroying by
projective measurement) the coherence of the ensemble pseudo-spin of atoms over
many measurement cycles. This scheme uses weak measurement to monitor the phase
in Ramsey method and repeat the cycle without initialization of phase and we
call, "atomic phase lock (APL)" in this paper. APL will achieve white phase
noise as long as the noise accumulated during dead time and the decoherence are
smaller than the measurement noise. A numerical simulation confirms that with
APL, Allan deviation is averaged down at a maximum rate that is proportional to
the inverse of total measurement time, tau^-1. In contrast, the current atomic
clocks that use projection measurement suppress the noise only down to the
level of white frequency, in which case Allan deviation scales as tau^-1/2.
Faraday rotation is one of the possible ways to realize weak measurement for
APL. We evaluate the strength of Faraday rotation with 171Yb+ ions trapped in a
linear rf-trap and discuss the performance of APL. The main source of the
decoherence is a spontaneous emission induced by the probe beam for Faraday
rotation measurement. One can repeat the Faraday rotation measurement until the
decoherence become comparable to the SNR of measurement. We estimate this
number of cycles to be ~100 cycles for a realistic experimental parameter.Comment: 18 pages, 7 figures, submitted to New Journal of Physic
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