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Category: quantum physics

One-way phonon synchronization could survive noise and defects, theoretical physicists suggest

A novel approach for realizing the one-way quantum synchronization of phonons has been proposed by three theoretical physicists at RIKEN. Importantly, this method is remarkably resilient against practical challenges such as imperfections and environmental noise. Their paper, “Nonreciprocal quantum synchronization,” is published in Nature Communications.

Many devices use components that act as one-way streets, allowing particles to travel in one direction, but almost not at all in the opposite one. These so-called nonreciprocal components are widely used in microwave and light-based systems for things such as controlling signal flow and preventing reflections.

“Nonreciprocal components enable signals to travel along desired paths, whereas they are strongly attenuated in the opposite direction,” notes Franco Nori of the RIKEN Center for Quantum Computing (RQC). “This ability finds applications ranging from signal processing to invisible cloaking.”

Quantum ‘dark modes’ no longer block phonon control, opening new paths for scalable devices

Three RIKEN researchers have demonstrated a way to stop problematic “dark modes” from squelching intriguing effects in quantum systems. This advance could help with the development of more versatile quantum devices that can be used to control the storage and transmission of quantum information. The study is published in the journal Nature Communications.

Manipulations that alter the topology of certain quantum systems known as non-Hermitian systems are attracting increasing attention, since they offer novel possibilities for manipulating particles of sound (phonons) and light (photons) as well as other excitations.

“Topological operations allow for various weird and fascinating phenomena, such as the buildup of chiral phases and the movement of phonons in one direction,” notes Franco Nori of the RIKEN Center for Quantum Computing (RQC).

Quantum Simulations Now Model Energy Loss With Greater Accuracy

A new computational technique accurately models decoherence’s impact on light–matter interactions within waveguide quantum electrodynamics. Matias Bundgaard-Nielsen and colleagues at the Technical University of Denmark present a matrix product state (MPS) method capable of modelling decoherence processes via density matrices, representing a key advancement over previous approaches. The method utilises collision quantum optics and efficiently incorporates various loss mechanisms, including emitter pure dephasing and off-chip radiative decay, to simulate complex waveguide QED systems such as two-level systems and multi-emitter setups. By modelling these realistic dissipation dynamics, the research offers vital insights into the behaviour of quantum systems and enables improved designs for quantum technologies.

A six-fold increase in simulated timescales for waveguide quantum electrodynamics has been achieved, surpassing limitations that previously restricted simulations to Markovian dynamics. This advancement results from employing a density matrix-based matrix product state (MPS) method, enabling accurate modelling of non-Markovian effects arising from time delays and memory effects within the system.

Traditionally, waveguide QED simulations have relied on the Markov approximation, which assumes that the system’s memory of past events is negligible. However, in many realistic scenarios—particularly those involving long propagation delays within the waveguide or slow emitter dynamics—this approximation breaks down. The method explicitly accounts for the system’s history, allowing the simulation of phenomena that depend on non-Markovian effects. In particular, it incorporates realistic decoherence mechanisms such as pure dephasing, which perturbs the phase coherence of quantum states, and off-chip radiative decay, where excitation energy is lost to the environment outside the waveguide.

New study bridges the worlds of classical and quantum physics

When you throw a ball in the air, the equations of classical physics will tell you exactly what path the ball will take as it falls, and when and where it will land. But if you were to squeeze that same ball down to the size of an atom or smaller, it would behave in ways beyond anything that classical physics can predict.

Or so we’ve thought.

MIT scientists have now shown that certain mathematical ideas from everyday classical physics can be used to describe the often weird and nonintuitive behavior that occurs at the quantum, subatomic scale.

Ion Clock Experiments Reveal Time Can Go Quantum

PRESS RELEASE — Few concepts in physics are as familiar, yet as enigmatic, as time. In Einstein’s theory of relativity, time is not absolute: its passage depends on motion and gravity. But when combined with quantum physics, this relativistic form of time becomes even more counterintuitive. According to quantum theory, the flow of time itself may exist in a genuine quantum superposition, ticking faster and slower at the same time. Now, a new paper titled Quantum signatures of proper time in optical ion clocks, published on April 20, 2026 in Physical Review Letters, the premier physics research journal, shows that this striking possibility may soon be tested in the laboratory.

In this work, a team led by Assistant Professor of theoretical physics Igor Pikovski at Stevens Institute of Technology, in collaboration with experimental groups of Christian Sanner at Colorado State University and Dietrich Leibfried at the National Institute of Standards and Technology (NIST), explores quantum aspects of the flow of time and how they can be accessed with atomic clocks. Their results suggest that the same quantum technologies being developed for next-generation clocks and quantum computers may soon probe something far more fundamental: When a clock’s motion obeys quantum mechanics, its movement can exist in superposition, and with it the recorded passage of time itself. This is analogous to Schrödinger’s famous thought experiment, where the counterintuitive nature of quantum superposition is illustrated by a cat being both alive and dead; here it is the passage of time itself that is in superposition, like a cat that is both young and old at once.

“Time plays very different roles in quantum theory and in relativity,” says Pikovski. “What we show is that bringing these two concepts together can reveal hidden quantum signatures of time-flow that can no longer be described by classical physics.”

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