Quantum sensing in your pocket
Using OLEDs to image magnetic fields
Peer-Reviewed PublicationIMAGE: AN ILLUSTRATION OF THE SPATIALLY-RESOLVED ODMR (OPTICALLY DETECTED MAGNETIC RESONANCE) SYSTEM FOR MAGNETIC FIELD IMAGING. view more
CREDIT: EXCITON SCIENCE
Smartphones could one day become portable quantum sensors thanks to a new chip-scale approach that uses organic light-emitting diodes (OLEDs) to image magnetic fields.
Researchers from the ARC Centre of Excellence in Exciton Science at UNSW Sydney have demonstrated that OLEDs, a type of semiconductor material commonly found in flat-screen televisions, smartphone screens and other digital displays, can be used to map magnetic fields using magnetic resonance.
Sensing of magnetic fields has important applications in scientific research, industry and medicine.
Published in the prestigious journal Nature Communications, this technique is able to function at microchip scale and - unlike other common approaches – does not require input from a laser.
The majority of existing quantum sensing and magnetic field imaging equipment is relatively large and expensive, requiring either optical pumping (from a high-powered laser) or very low cryogenic temperatures. This limits the device integration potential and commercial scalability of such approaches.
By contrast, the OLED sensing device prototyped in this work would ultimately be small, flexible and mass-producible.
The techniques involved in achieving this are electrically detected magnetic resonance (EDMR) and optically detected magnetic resonance (ODMR). This is achieved using a camera and microwave electronics to optically detect magnetic resonance, the same physics which enables Magnetic Resonance Imaging (MRI).
Using OLEDs for EDMR and ODMR depends on correctly harnessing the spin behaviour of electrons when they are in proximity to magnetic fields.
OLEDs, which are highly sensitive to magnetic fields, are already found in mass-produced electronics like televisions and smartphones, making them an attractive prospect for commercial development in new technologies.
Professor Dane McCamey of UNSW, who is also an Exciton Science Chief Investigator, said: “Our device is designed to be compatible with commercially available OLED technologies, providing the unique ability to map magnetic field over a large area or even a curved surface.
“You could imagine using this technology being added to smartphones to help with remote medical diagnostics, or identifying defects in materials.”
First author Dr Rugang Geng of UNSW and Exciton Science added: “While our study demonstrates a clear technology pathway, more work will be required to increase the sensitivity and readout times.”
Professor McCamey said that a patent has been filed (Australian Patent Application 2022901738) with a view toward potential commercialisation of the technology.
Dr Rugang Geng working at UNSW Sydney.
CREDIT
Exciton Science
JOURNAL
Nature
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Sub-micron spin-based magnetic field imaging with an organic light emitting diode
COI STATEMENT
The authors, through the University of New South Wales, have applied for a patent related to this work (Australian Patent Application 2022901738). All authors are inventors, and no other inventors are named.
Paradoxical quantum phenomenon measured for the first time
How do quantum particles share information? A peculiar conjecture about quantum information has been experimentally confirmed at the TU Wien.
Peer-Reviewed PublicationIMAGE: VACUUM CHAMBER CONTAINING THE ATOM CHIP view more
CREDIT: THOMAS SCHWEIGLER, TU WIEN
Some things are related, others are not. Suppose you randomly select a person from a crowd who is significantly taller than the average. In that case, there is a good chance that they will also weigh more than the average. Statistically, one quantity also contains some information about the other.
Quantum physics allows for even stronger links between different quantities: different particles or parts of an extensive quantum system can "share" a certain amount of information. There are curious theoretical predictions about this: surprisingly, the measure of this "mutual information" does not depend on the size of the system but only on its surface. This surprising result has been confirmed experimentally at the TU Wien and published in Nature Physics. Theoretical input to the experiment and its interpretation came from the Max-Planck-Institut für Quantenoptik in Garching, FU Berlin, ETH Zürich and New York University.
Quantum information: More strongly connected than classical physics allows
"Let's imagine a gas container in which small particles fly around and behave in a very classical way like small spheres," says Mohammadamin Tajik of the Vienna Center for Quantum Science and Technology (VCQ) - Atominstitut of TU Wien, first author of the current publication. "If the system is in equilibrium, then particles in different areas of the container know nothing about each other. One can consider them completely independent of each other. Therefore, one can say that the mutual information these two particles share is zero."
In the quantum world, however, things are different: If particles behave quantumly, then it may happen that you can no longer consider them independently of each other. They are mathematically connected - you can't meaningfully describe one particle without saying something about the other.
"For such cases, there has long been a prediction about the mutual information shared between different subsystems of a many-body quantum system," explains Mohammadamin Tajik. "In such a quantum gas, the shared mutual information is larger than zero, and it does not depend on the size of the subsystems - but only on the outer bounding surface of the subsystem."
This prediction seems intuitively strange: In the classical world, it is different. For example, the information contained in a book depends on its volume - not merely on the area of the book's cover. In the quantum world, however, information is often closely linked to surface area.
Measurements with ultracold atoms
An international research team led by Prof. Jörg Schmiedmayer has now confirmed for the first time that the mutual information in a many body quantum system scales with the surface area rather than with the volume. For this purpose, they studied a cloud of ultracold atoms. The particles were cooled to just above absolute zero temperature and held in place by an atom chip. At extremely low temperatures, the quantum properties of the particles become increasingly important. The information spreads out more and more in the system, and the connection between the individual parts of the overall system becomes more and more significant. In this case, the system can be described with a quantum field theory.
"The experiment is very challenging," says Jörg Schmiedmayer. "We need complete information about our quantum system, as best as quantum physics allows. For this, we have developed a special tomography technique. We get the information we need by perturbing the atoms just a bit and then observing the resulting dynamics. It's like throwing a rock into a pond and then getting information about the state of the liquid and the pond from the consequent waves."
As long as the system's temperature does not reach absolute zero (which is impossible), this "shared information" has a limited range. In quantum physics, this is related to the "coherence length" - it indicates the distance to which particles quantumly behave similar, and thereby know from each other. "This also explains why shared information doesn't matter in a classical gas," says Mohammadamin Tajik. "In a classical many-body system, coherence disappears; you can say the particles no longer know anything about their neighboring particles." The effect of temperature and coherence length on mutual information was also confirmed in the experiment.
Quantum information plays an essential role in many technical applications of quantum physics today. Thus, the experiment results are relevant to various research areas - from solid-state physics to the quantum physical study of gravity.
JOURNAL
Nature Physics
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Verification of the area law of mutual information in a quantum field simulator
ARTICLE PUBLICATION DATE
24-Apr-2023
Using quantum physics to secure wireless devices
New paper from UIC Engineering published in Nature Communications
Peer-Reviewed PublicationFrom access cards and key fobs to Bluetooth speakers, the security of communication between wireless devices is critical to maintaining privacy and preventing theft. Unfortunately, these tools are not foolproof and information on how to hack, clone and bypass these systems is becoming easier to find.
That’s why computer engineers at the University of Illinois Chicago have been investigating ways to create more secure devices. In a new paper, UIC scientists report a method inspired by quantum physics to improve wireless device identification and protect device-to-device communication. It uses a truly random and unique digital fingerprint to create a hardware encryption system that is virtually unbreakable.
The scientists, led by Pai-Yen Chen, used a theory from quantum physics in math-based experiments to identify a “divergent exceptional point.”
Quantum physics describes systems for which precise measurement is difficult or impossible; a quantum state describes a parameter space or range of possible measurements. Within these states, there exist exceptional points where the uncertainty of the system is at its maximum. These points are promising for cryptography — the more uncertain the system, the more secure.
Chen and colleagues figured out a mathematical approach to identify these exceptional points in a radio frequency identification system — the technology used by key cards, fobs and other devices that unlock or communicate with nearby sensors. In traditional RFID systems, encrypted keys are stored inside memory chips, which are limited in size and vulnerable to attack.
Chen’s group created new RFID lock-and-tag devices that utilize the exceptional point algorithm to create a secure signal. Since every piece of hardware is slightly different due to small variations during the fabrication process, each RFID device produces its own unique digital fingerprint in light of the maximized uncertainty at the exceptional point.
Like each individual’s voice — which is heard via analog sound waves — their key cryptography structure makes the signal from each device unique, Chen said.
After thousands of simulations, they could not find two identical digital fingerprints, passing National Institute of Standards and Technology randomness tests and machine learning-based attacks.
“Many scientists have thought that the exceptional point theory would be impossible to apply reliably in the real world, but we were able to leverage such a property to implement a novel system,” said Chen, associate professor of electrical and computer engineering at the UIC College of Engineering. “In this paper, we proposed a new circuit with a divergent exceptional point to significantly improve the uniqueness, randomness and robustness of an electromagnetic physically unclonable function.”
“This lightweight and robust analog PUF structure may lead to a variety of unforeseen securities and anti-counterfeiting applications in radio-frequency fingerprinting and wireless communications,” the authors write.
Chen said that the technology is also low cost and highly versatile, which is why it could be particularly helpful for products, such as key cards and near-field communication devices, that are mass-produced and more vulnerable to hacks.
“We simply used the standard printed circuit board fabrication process, suitable for low-cost and mass production. The improved security lies in carefully designing the radio frequency circuit to operate around the exceptional point, which we demonstrated with a wireless identification system,” Chen said.
“Spectral sensitivity near exceptional points as a resource for hardware encryption” is published in Nature Communications. Co-authors of the study include Minye Yang and Liang Zhu of UIC, and Qi Zhong and R. El-Ganainy of Michigan Technological University. The research has been supported, in part, by grants from the National Science Foundation (ECCS1914420) and the Air Force Office of Scientific Research (FA95502110202).
JOURNAL
Nature Communications
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Spectral sensitivity near exceptional points as a resource for hardware encryption
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