Controlling signal routing in quantum information processing

Date:
July 13, 2023
Source:
University of Vienna
Summary:
Routing signals and isolating them against noise and
back-reflections are essential in many practical situations in
classical communication as well as in quantum processing. In
a theory-experimental collaboration, a team has achieved
unidirectional transport of signals in pairs of 'one-way
streets'. This research opens up new possibilities for more flexible
signaling devices.


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FULL STORY ========================================================================== Routing signals and isolating them against noise and back-reflections
are essential in many practical situations in classical communication as
well as in quantum processing. In a theory-experimental collaboration,
a team led by Andreas Nunnenkamp from the University of Vienna and Ewold Verhagen based at the research institute AMOLF in Amsterdam has achieved unidirectional transport of signals in pairs of "one-way streets." This research published in Nature Physics opens up new possibilities for more flexible signaling devices.

Devices that allow to route signals, for example carried by light or
sound waves, are essential in many practical situations. This is, for
instance, the case in quantum information processing, where the states
of the quantum computer have to be amplified to read them out -- without
noise from the amplification process corrupting them. That is why devices
that allow signals to travel in a one-way channel e.g. isolators or
circulators are much sought- after. However, at present such devices are
lossy, bulky, and require large magnetic fields that break time-reversal symmetry to achieve unidirectional behaviour. These limitations have
prompted strong efforts to find alternatives that take less space and
that do not rely on magnetic fields.

The new study published in Nature Physicsintroduces a new class of
systems characterized by a phenomenon the authors call "quadrature nonreciprocity." Quadrature nonreciprocity exploits interference between
two distinct physical processes. Each of the processes produces a wave
that contributes to the transmitted signal. Like water waves produced
by two thrown pebbles, the two waves can either cancel or amplify each
other, in a phenomenon known as interference.

This allows for unidirectional transmission of signals without
time-reversal breaking and leads to a distinctive dependence on
the phase, i.e., the quadrature, of the signal. "In these devices,
transmission depends not only on the direction of the signal, but also
on the signal quadrature" says Clara Wanjura, the theoretical lead
author of the study. "This realizes a 'dual carriageway' for signals:
one quadrature is transmitted in one direction and the other quadrature
in the opposite direction. Time-reversal symmetry then enforces that
the quadratures always travel pairwise along opposite directions in two separate lanes." The experimental team at AMOLF has demonstrated this phenomenon experimentally in a nanomechanical system where interactions
among mechanical vibrations of small silicon strings are orchestrated by
laser light. Laser light exerts forces on the strings, thereby mediating interactions between their different vibration 'tones'. Jesse Slim,
the experimental lead author of the study says: "We have developed
a versatile experimental toolbox that allowed us to control the two
different types of interactions that are needed to implement quadrature nonreciprocity. This way we could reveal the resulting unidirectional
transport of the signals experimentally." The work opens up new
possibilities for signal routing and quantum-limited amplification,
with potential applications in quantum information processing and sensing.

* RELATED_TOPICS
o Matter_&_Energy
# Physics # Quantum_Physics # Spintronics # Optics
o Computers_&_Math
# Quantum_Computers # Spintronics_Research #
Computers_and_Internet # Encryption
* RELATED_TERMS
o Physics o Transport o Quantum_computer o John_von_Neumann
o Quantum_entanglement o Introduction_to_quantum_mechanics o
Uncertainty_principle o Supercomputer

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========================================================================== Journal Reference:
1. Clara C. Wanjura, Jesse J. Slim, Javier del Pino, Matteo Brunelli,
Ewold
Verhagen, Andreas Nunnenkamp. Quadrature nonreciprocity in bosonic
networks without breaking time-reversal symmetry. Nature Physics,
2023; DOI: 10.1038/s41567-023-02128-x ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230713141937.htm

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