458 research outputs found
Classical many-body time crystals
Discrete time crystals are a many-body state of matter where the extensive
system's dynamics are slower than the forces acting on it. Nowadays, there is a
growing debate regarding the specific properties required to demonstrate such a
many-body state, alongside several experimental realizations. In this work, we
provide a simple and pedagogical framework by which to obtain many-body time
crystals using parametrically coupled resonators. In our analysis, we use
classical period-doubling bifurcation theory and present a clear distinction
between single-mode time-translation symmetry breaking and a situation where an
extensive number of degrees of freedom undergo the transition. We
experimentally demonstrate this paradigm using coupled mechanical oscillators,
thus providing a clear route for time crystals realizations in real materials.Comment: 23 pages, 5 figures, comments are welcom
The role of fluctuations in quantum and classical time crystals
Discrete time crystals (DTCs) are a many-body state of matter whose dynamics
are slower than the forces acting on it. The same is true for classical systems
with period-doubling bifurcations. Hence, the question naturally arises what
differentiates classical from quantum DTCs. Here, we analyze a variant of the
Bose-Hubbard model, which describes a plethora of physical phenomena and has
both a classical and a quantum time-crystalline limit. We study the role of
fluctuations on the stability of the system and find no distinction between
quantum and classical DTCs. This allows us to probe the fluctuations in an
experiment using two strongly coupled parametric resonators subject to
classical noise.Comment: 11 pages, 5 figure
Rapid flipping of parametric phase states
Since the invention of the solid-state transistor, the overwhelming majority
of computers followed the von Neumann architecture that strictly separates
logic operations and memory. Today, there is a revived interest in alternative
computation models accompanied by the necessity to develop corresponding
hardware architectures. The Ising machine, for example, is a variant of the
celebrated Hopfield network based on the Ising model. It can be realized with
artifcial spins such as the `parametron' that arises in driven nonlinear
resonators. The parametron encodes binary information in the phase state of its
oscillation. It enables, in principle, logic operations without energy transfer
and the corresponding speed limitations. In this work, we experimentally
demonstrate flipping of parametron phase states on a timescale of an
oscillation period, much faster than the ringdown time \tau that is often
(erroneously) deemed a fundamental limit for resonator operations. Our work
establishes a new paradigm for resonator-based logic architectures.Comment: 6 pages, 3 figure
Ghost in the Ising machine
Coupled nonlinear systems have promise for parallel computing architectures.
En route to realizing complex networks for Ising machines, we report an
experimental and theoretical study of two coupled parametric resonators
(parametrons). The coupling severely impacts the bifurcation topology and the
number of available solutions of the system; in part of the stability diagram,
we can access fewer solutions than expected. When applying noise to probe the
stability of the states, we find that the switching rates and the phase-space
trajectories of the system depend on the detuning in surprising ways. We
present a theoretical framework that heralds the existence of 'ghost
bifurcations'. These bifurcations involve only unstable solutions and lead to
avoided zones in phase space. The emergence of such ghost bifurcations is an
important feature of parametron networks that can influence their application
for parallel logic operations
A parametric symmetry breaking transducer
Force detectors rely on resonators to transduce forces into a readable
signal. Usually these resonators operate in the linear regime and their signal
appears amidst a competing background comprising thermal or quantum
fluctuations as well as readout noise. Here, we demonstrate that a parametric
symmetry breaking transduction leads to a novel and robust nonlinear force
detection in the presence of noise. The force signal is encoded in the
frequency at which the system jumps between two phase states which are
inherently protected against phase noise. Consequently, the transduction
effectively decouples from readout noise channels. For a controlled
demonstration of the method, we experiment with a macroscopic doubly-clamped
string. Our method provides a promising new paradigm for high-precision force
detection.Comment: 7 pages, 5 figure
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