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Insight into Quantum States - Possible Key to Quantum Computers

A new study offers an insight into a recent experiment that was able to control an exceptional number of atoms via a quantum simulator. The experiment conducted by Harvard University and MIT created a specialized quantum computer, termed as a quantum simulator, which could be used to help comprehend intricate quantum processes.

Illustration of quantum system. (Image credit: Zlatko Papic, University of Leeds)

The study, led by the University of Leeds, has provided a theoretical justification for the specific behavior of individual atoms that were captured and manipulated in the experiment.

Manipulating Quantum Bits of Matter

The Harvard University and MIT experiment employed a system of exceptionally tuned lasers to serve as “optical tweezers” to assemble an extraordinarily long chain of 51 atoms. When the quantum dynamics of the atom chain were calculated, there were unexpected oscillations that persisted for a lot longer than anticipated and which could not be explained.

The international team of scientists investigating the behavior included researchers from the School of Physics and Astronomy, the Institute of Science and Technology Austria and the University of Geneva.

Study co-author, Dr. Zlatko Papic, Lecturer in Theoretical Physics at Leeds, said: “The previous Harvard-MIT experiment created surprisingly robust oscillations that kept the atoms in a quantum state for an extended time.

"We found these oscillations to be rather puzzling because they suggested that atoms were somehow able to 'remember' their initial configuration while still moving chaotically.

“Our goal was to understand more generally where such oscillations could come from since oscillations signify some kind of coherence in a chaotic environment – and this is precisely what we want from a robust quantum computer.

"Our work suggests that these oscillations are due to a new physical phenomenon that we called ‘quantum many-body scar’.”

Deeper Understanding of Quantum Dynamics

In daily life, particles will leap off one another until they explore the whole space, settling ultimately into a state of equilibrium. This process is referred to as thermalization.

A quantum scar is when a distinct configuration or pathway leaves a stamp on the particles’ state that prevents them from filling the whole space. This keeps the systems from reaching thermalization and allows them to preserve some quantum effects.

Dr. Papic said: “We are learning that quantum dynamics can be much more complex and intricate than simply thermalization.

"The practical benefit is that extended periods of oscillations are exactly what is needed if quantum computers are to become a reality.

"The information processed and stored on these computers will be dependent on keeping the atoms in more than one state at any time, it is a constant battle to keep the particles from settling into an equilibrium.”

Previous theories involving quantum scars have been formulated for a single particle. Our work has extended these ideas to systems which contain not one but many particles, which are all entangled with each other in complicated ways.

Quantum many-body scars might represent a new avenue to realize coherent quantum dynamics.

Christopher Turner, Study Lead Author & Doctoral Researcher at the School of Physics & Astronomy at Leeds

The quantum many-body scars theory offers insights on the quantum states that underpin the odd dynamics of atoms in the Harvard-MIT experiment.

Understanding this occurrence could also make way for shielding or prolonging the lifetime of quantum states in other groups of quantum many-body systems.

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