20 research outputs found
Exploring quantum chaos with a single nuclear spin
Most classical dynamical systems are chaotic. The trajectories of two
identical systems prepared in infinitesimally different initial conditions
diverge exponentially with time. Quantum systems, instead, exhibit
quasi-periodicity due to their discrete spectrum. Nonetheless, the dynamics of
quantum systems whose classical counterparts are chaotic are expected to show
some features that resemble chaotic motion. Among the many controversial
aspects of the quantum-classical boundary, the emergence of chaos remains among
the least experimentally verified. Time-resolved observations of quantum
chaotic dynamics are particularly rare, and as yet unachieved in a single
particle, where the subtle interplay between chaos and quantum measurement
could be explored at its deepest levels. We present here a realistic proposal
to construct a chaotic driven top from the nuclear spin of a single donor atom
in silicon, in the presence of a nuclear quadrupole interaction. This system is
exquisitely measurable and controllable, and possesses extremely long intrinsic
quantum coherence times, allowing for the observation of subtle dynamical
behavior over extended periods. We show that signatures of chaos are expected
to arise for experimentally realizable parameters of the system, allowing the
study of the relation between quantum decoherence and classical chaos, and the
observation of dynamical tunneling.Comment: revised and published versio
Selective Single and Double-Mode Quantum Limited Amplifier
A quantum-limited amplifier enables the amplification of weak signals while
introducing minimal noise dictated by the principles of quantum mechanics.
These amplifiers serve a broad spectrum of applications in quantum computing,
including fast and accurate readout of superconducting qubits and spins, as
well as various uses in quantum sensing and metrology. Parametric
amplification, primarily developed using Josephson junctions, has evolved into
the leading technology for highly effective microwave measurements within
quantum circuits. Despite their significant contributions, these amplifiers
face fundamental limitations, such as their inability to handle high powers,
sensitivity to parasitic magnetic fields, and particularly their limitation to
operate only at millikelvin temperatures. To tackle these challenges, here we
experimentally develop a novel quantum-limited amplifier based on
superconducting kinetic inductance and present an extensive theoretical model
to describe this nonlinear coupled-mode system. Our device surpasses the
conventional constraints associated with Josephson junction amplifiers by
operating at much higher temperatures up to 4.5 K. With two distinct spectral
modes and tunability through bias current, this amplifier can operate
selectively in both single and double-mode amplification regimes near the
quantum noise limit. Utilizing a nonlinear thin film exhibiting kinetic
inductance, our device attains gain exceeding 50 dB in a single-mode and 32 dB
in a double-mode configuration while adding 0.35 input-referred quanta of
noise. Importantly, this amplifier eliminates the need for Josephson junctions,
resulting in significantly higher power handling capabilities than
Josephson-based amplifiers. It also demonstrates resilience in the presence of
magnetic fields, offers a straightforward design, and enhances reliability
Strong Microwave Squeezing Above 1 Tesla and 1 Kelvin
Squeezed states of light have been used extensively to increase the precision
of measurements, from the detection of gravitational waves to the search for
dark matter. In the optical domain, high levels of vacuum noise squeezing are
possible due to the availability of low loss optical components and
high-performance squeezers. At microwave frequencies, however, limitations of
the squeezing devices and the high insertion loss of microwave components makes
squeezing vacuum noise an exceptionally difficult task. Here we demonstrate a
new record for the direct measurement of microwave squeezing. We use an ultra
low loss setup and weakly-nonlinear kinetic inductance parametric amplifiers to
squeeze microwave noise 7.8(2) dB below the vacuum level. The amplifiers
exhibit a resilience to magnetic fields and permit the demonstration of record
squeezing levels inside fields of up to 2 T. Finally, we exploit the high
critical temperature of our amplifiers to squeeze a warm thermal environment,
achieving vacuum level noise at a temperature of 1.8 K. These results enable
experiments that combine squeezing with magnetic fields and permit
quantum-limited microwave measurements at elevated temperatures, significantly
reducing the complexity and cost of the cryogenic systems required for such
experiments.Comment: Main text: 9 pages, 4 figures. Supplementary information: 21 pages,
17 figure
Coherent control of NV- centers in diamond in a quantum teaching lab
The room temperature compatibility of the negatively-charged nitrogen-vacancy
(NV-) in diamond makes it the ideal quantum system for a university teaching
lab. Here, we describe a low-cost experimental setup for coherent control
experiments on the electronic spin state of the NV- center. We implement
spin-relaxation measurements, optically-detected magnetic resonance, Rabi
oscillations, and dynamical decoupling sequences on an ensemble of NV- centers.
The relatively short times required to perform each of these experiments (<10
minutes) demonstrate the feasibility of the setup in a teaching lab. Learning
outcomes include basic understanding of quantum spin systems, magnetic
resonance, the rotating frame, Bloch spheres, and pulse sequence development.Comment: 16 pages, 9 figure
Observing hyperfine interactions of NV centers in diamond in an advanced quantum teaching lab
The negatively charged nitrogen-vacancy (NV) center in diamond is a model
quantum system for university teaching labs due to its room-temperature
compatibility and cost-effective operation. Based on the low-cost experimental
setup that we have developed and described for the coherent control of the
electronic spin (Sewani et al.), we introduce and explain here a number of more
advanced experiments that probe the electron-nuclear interaction between the
\nv electronic and the \NN~and \CC~nuclear spins. Optically-detected magnetic
resonance (ODMR), Rabi oscillations, Ramsey fringe experiments, and Hahn echo
sequences are implemented to demonstrate how the nuclear spins interact with
the electron spins. Most experiments only require 15 minutes of measurement
time and can, therefore, be completed within one teaching lab.Comment: Extension of the teaching lab experiments described in Sewani et al.,
Coherent control of NV centers in diamond in a quantum teaching lab. American
Journal of Physics 88, 1156 (2020). https://doi.org/10.1119/10.000190