Experimental demonstration of measurement-dependent realities possible, researcher says

February 16, 2021

Shoe shops sell a variety of shoe sizes to accommodate a variety of foot sizes -- but what if both the shoe and foot size depended on how it was measured? Recent developments in quantum theory suggest that the available values of a physical quantity, such as a foot size, can depend on the type of measurement used to determine them. If feet were governed by the laws of quantum mechanics, foot size would depend on the markings on a foot measure to find the best fit -- at the time of measurement -- and even if the markings were changed, the measurement could still be precise.

In quantum mechanics, the "size" of a physical quantity is more elusive than foot length because unavoidable uncertainties in the history of a quantum system make it difficult to confirm the measurement due to what's called the uncertainty principle. Essentially, it is impossible to know the real properties that a quantum system had before the measurement. There isn't a way to try on the shoe after the measurement -- until now. A researcher at Hiroshima University may have found a solution to the problem, with possible implications for emerging quantum information technologies, such as quantum communication and quantum computing.

Holger F. Hofmann, professor in the Graduate School of Advanced Science and Engineering, Hiroshima University, published his approach on Feb. 3 in Physical Review Research, a journal of the American Physical Society.

According to Hofmann, a qubit -- the basic unit of quantum information -- can be used as an external probe to test the precision of a measurement of a physical property in its original quantum system. The probe interacts weakly, creating a memory of the physical property that is automatically encrypted by the qubit. The quantum encrypted one qubit memory can be used to evaluate the precision of a subsequent measurement. A feedback design allows the later measurement value to erase the quantum memory encoded on the probe qubit. If the memory is perfectly erased without any leftover traces, Hofmann said, the measurement outcomes must have been precise each and every time the measurement was performed.

This experimental procedure to probe the amount of uncertainty in a measurement result allows researchers to demonstrate that different measurements can accurately determine the same physical property of a quantum system before the measurement happened -- even when the values of the physical property change based on the measurement procedure, according to Hofmann.

"Quantum mechanics describes physical systems as mysterious 'super positions' of possibilities that seemingly 'collapse' into reality only when a measurement distinguishes the different possibilities," Hofmann said, referring to the idea that mere observation fundamentally changes a system. "There have been many attempts to find out what is there when nobody is looking, and my work builds on these previous attempts."

Hofmann noted that these attempts involve unmeasurable, unobservable uncertainties, making it difficult to answer any questions about the fundamental nature of reality.

"There is still a lot to do, and I hope that many members of the quantum measurement community will join in to develop the necessary theoretical framework," Hofmann said. "Physics should be grounded in observable phenomena, but, strangely enough, the concepts used in quantum mechanics are not."
-end-
About Hiroshima University

Since its foundation in 1949, Hiroshima University has striven to become one of the most prominent and comprehensive universities in Japan for the promotion and development of scholarship and education. Consisting of 12 schools for undergraduate level and 4 graduate schools, ranging from natural sciences to humanities and social sciences, the university has grown into one of the most distinguished comprehensive research universities in Japan. English website: https://www.hiroshima-u.ac.jp/en

Hiroshima University

Related Memory Articles from Brightsurf:

Memory of the Venus flytrap
In a study to be published in Nature Plants, a graduate student Mr.

Memory protein
When UC Santa Barbara materials scientist Omar Saleh and graduate student Ian Morgan sought to understand the mechanical behaviors of disordered proteins in the lab, they expected that after being stretched, one particular model protein would snap back instantaneously, like a rubber band.

Previously claimed memory boosting font 'Sans Forgetica' does not actually boost memory
It was previously claimed that the font Sans Forgetica could enhance people's memory for information, however researchers from the University of Warwick and the University of Waikato, New Zealand, have found after carrying out numerous experiments that the font does not enhance memory.

Memory boost with just one look
HRL Laboratories, LLC, researchers have published results showing that targeted transcranial electrical stimulation during slow-wave sleep can improve metamemories of specific episodes by 20% after only one viewing of the episode, compared to controls.

VR is not suited to visual memory?!
Toyohashi university of technology researcher and a research team at Tokyo Denki University have found that virtual reality (VR) may interfere with visual memory.

The genetic signature of memory
Despite their importance in memory, the human cortex and subcortex display a distinct collection of 'gene signatures.' The work recently published in eNeuro increases our understanding of how the brain creates memories and identifies potential genes for further investigation.

How long does memory last? For shape memory alloys, the longer the better
Scientists captured live action details of the phase transitions of shape memory alloys, giving them a better idea how to improve their properties for applications.

A NEAT discovery about memory
UAB researchers say over expression of NEAT1, an noncoding RNA, appears to diminish the ability of older brains to form memories.

Molecular memory can be used to increase the memory capacity of hard disks
Researchers at the University of Jyväskylä have taken part in an international British-Finnish-Chinese collaboration where the first molecule capable of remembering the direction of a magnetic above liquid nitrogen temperatures has been prepared and characterized.

Memory transferred between snails
Memories can be transferred between organisms by extracting ribonucleic acid (RNA) from a trained animal and injecting it into an untrained animal, as demonstrated in a study of sea snails published in eNeuro.

Read More: Memory News and Memory Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.