The Thinking Beyond webinar, "What happens when a quantum measurement is made?" held on Feb. 26, focused on the intricacies of quantum measurements and their implications for understanding the quantum world.
This session, part of a series on cutting edge scientific topics, delved into how quantum measurements bridge classical mechanics and the probabilistic nature of quantum mechanics, a challenge that has intrigued scientists for nearly a century.
Hosted by the Thinking Beyond initiative of the Beyond Center, the webinar featured Andrew Jordan, co-director of the Institute for Quantum Studies and professor of physics at Chapman University, as the guest speaker.
He was joined by Paul Davies, a regents professor at the Department of Physics and the Beyond Center, and Maulik Parikh, a professor at the Department of Physics and the Beyond Center, to present and discuss the topic of quantum measurements.
Jordan mainly presented the topics and motivations of his recently published book, "Quantum Measurement: Theory and Practice," including experiments that produce quantum measurements, physical applications of quantum technology and theoretical implications.
Experimentation
Quantum measurements differ from classical measurements mainly in their capabilities; while classical experiments are performed with minimal invasions of the target system, they are limited in other aspects. Mainly, they are irreversible, instantaneous and projective, creating disturbances to the system and failing to accurately capture its behavior.
"(What's) exciting is that these (quantum measurements) can break all three of these properties," Jordan said. "They can take place over a period of time, they can be probabilistically reversed, and they can be minimally disturbing."
One application of these measurements is the Josephson junction, an important part of quantum computing.
"If you take, for example, a piece of aluminum and you make a junction with another piece of aluminum, (with) some oxide in between, that becomes the building block of a new kind of quantum circuit, the so-called Josephson junction quantum circuits," Jordan said.
This development represents a leap forward in creating more efficient and powerful quantum computing systems, leveraging the unique microscopic properties of materials.
Another important effect in quantum physics is the wave function collapse, which can prevent classical measurements from being made after a system is disturbed. The exploration of wave function collapse provides a deeper understanding of quantum behavior.
"This concept of wave function collapse actually can become a continuous process, so we can actually monitor how the wave function is collapsing as we're monitoring the quantum system," Jordan said.
This continuous observation allows scientists to gain unprecedented insight into the dynamics of quantum systems, potentially leading to more precise control and manipulation of quantum states.
Physical Applications
This webinar not only provided a platform for discussing advanced topics in quantum physics but also highlighted the importance of integrating experimental findings with theoretical frameworks, such as quantum entanglement, which contributes to the uniqueness of quantum states.
"One of the things I do think is very important in terms of quantum technology is building a reliable quantum link that keeps two things entangled indefinitely without degrading over time," Jordan said.
By maintaining entangled states over time without degradation, it becomes possible to achieve more secure quantum communication networks and advance the field of quantum computing.
The importance of establishing a reliable quantum link underscores the critical role of quantum entanglement in the development of quantum technologies.
Another one of these applications includes quantum amplifiers.
"(Quantum amplifiers are) taking very weak microwave-frequency electromagnetic radiation signals (and) putting it into amplifiers that are able to operate (at) the quantum limit," Jordan said.
By operating at the quantum limit, these amplifiers minimize noise and maximize signal integrity, which is crucial for the accuracy and reliability of quantum measurements and applications.
The creation of quantum-limited amplifiers marks a pivotal advancement in enhancing the capability to measure and manipulate quantum systems.
Theoretical Implications
The dialogue then ventured into the foundational concepts of reality, such as the potential for post-quantum scientific theory, that could reveal even stranger aspects of the universe than are currently understood.
"Our prediction is that if we find such a theory, it will not restore our notion of classical reality, of pre-existing things having properties before we measure them," Jordan said. "Our prediction is it will be even weirder than quantum mechanics."
Using the lens of classical physics, quantum measurements seem impossible, which is stipulated by Bell's theorem; however, research has broken that barrier.
"Based on the experiments that were done, (Bell's theorem), his inequality was violated," Jordan said.
The violation of Bell's theorem challenges fundamental assumptions about the nature of reality and the behavior of quantum systems. This pivotal discovery has profound implications for the interpretation of quantum mechanics, suggesting that quantum phenomena cannot be fully explained by classical physics or hidden variables theories.
The speculation on post-quantum science introduces the intriguing possibility of uncovering a deeper, more complex layer of reality beyond our current understanding.
Looking Ahead
"In the early days, I used to think (quantum mechanics) was really just a little bit of intellectual farm," Davies said. "A very old friend of mine, David Deutsch is to be the founder of quantum computing ... he was obsessed about the many universes interpretation of quantum mechanics. He invented the idea of the quantum computer as a way of testing whether there are these parallel realities."
The fascination with quantum computing transitioned from theoretical musings to a tangible pursuit as the field evolved.
"Decades went by, and it didn't really look like anything was going to happen," Davies said. "Then the technology got to the point where people really could make qubits."
From there, the software was developed to be able to utilize these qubits to create quantum computers.
"Suddenly, people paid attention, because it looked like there could be an arms race between different nations to get to the quantum computer first," Davies said.
This trend demonstrates the ever-evolving nature of the field, emphasizing the importance of informative conferences to keep both professionals and students up-to-date.
The Feb. 26 webinar was only one of the events that the Beyond Center has hosted. The following day, they hosted their annual in-person event with theoretical physicist Brian Greene, titled "Until the End of Time," which explored the past and future of the cosmos.
The next webinar, on March 25, will be titled "The dark matter in our genome," and will discuss DNA and biological information.
This session from the Thinking Beyond webinar series offers a compelling view into the ever-evolving field of quantum mechanics. As technology advances, the mysteries left to unravel remain vast and full of promise.
Edited by River Graziano, Sadie Buggle and Caera Learmonth.
Reach the reporter at dmanatou@asu.edu.
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