Tag: quantum mechanics

Light’s magnetic field influences matter, according to new findings by Israeli researchers, challenging long-held assumptions that light only illuminates matter and prompting a rethink of how the Faraday Effect works.

Some of today’s most cutting-edge technologies—currently mostly laboratory concepts such as spintronics and quantum devices—could benefit from this revised understanding, as the new work reexamines one of physics’ most fundamental interactions.

First discovered by Michael Faraday in 1845, the Faraday Effect describes what has long been viewed as an interaction solely between light’s electric field and matter. Observations of the effect reveal that light’s polarization rotates as it passes through a material exposed to a steady magnetic field. Traditionally, researchers believed only the electric field of light contributed to this rotation. Now, new work suggests that light’s magnetic field is also a significant player.

A new study provides theoretical evidence that the oscillating magnetic field of light directly contributes to the Faraday Effect. Dr. Amir Capua and Benjamin Assouline of the Institute of Electrical Engineering and Applied Physics at the Hebrew University of Jerusalem led the research, published in Nature Scientific Reports.

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Many of the most promising quantum technologies, including advanced sensors and future quantum computers, depend on a phenomenon known as entanglement, where particles become deeply connected and influence one another in ways that cannot be explained by classical physics. Creating the complex entangled states needed for these technologies has traditionally required sophisticated equipment and carefully designed experimental systems.

Researchers at the University of Chicago Pritzker School of Molecular Engineering have now proposed a much simpler approach. Their new theoretical method can generate and control a wide range of entangled quantum states using tools that are already common in many quantum physics laboratories.

The work, published in Physical Review X, could help advance ultra precise quantum sensing and open new opportunities for exploring fundamental physics.

“We wanted to take simple ingredients that you find in a lot of physical platforms and put these together in a minimal way to get something interesting, complex and powerful,” said Aashish Clerk, professor of molecular engineering at UChicago PME and senior author of the new study.

The research was supported by Q-NEXT, a U.S. Department of Energy National Quantum Information Science Research Center led by DOE’s Argonne National Laboratory.

Rethinking Cavity QED Systems

The team’s approach is based on cavity quantum electrodynamics, commonly known as cavity QED. In these experiments, atoms or other particles are placed inside an optical cavity, which consists of two mirrors that trap light between them. The particles then interact with the confined light inside the cavity.

A limitation of many cavity QED systems is that all of the atoms interact with the light in exactly the same way. Because the atoms are effectively indistinguishable, the range of quantum states that can be produced is restricted.

“The challenge has always been that these systems have too much symmetry. All the atoms are talking to light in the same way,” Clerk said. “That really restricts what kind of entangled states you get.”

In a typical cavity QED setup, each atom has a ground state and an excited state separated by a specific energy difference.

The researchers found a straightforward way to reduce the system’s symmetry. While all atoms continue to be driven by the same laser, additional lasers or magnetic fields are used to shift the excited state energies of different groups of atoms. The atoms are arranged so that each one is paired with another atom that has an equal but opposite energy offset.

This simple modification allows atoms to behave differently from one another while preserving enough structure for the system to remain controllable and predictable. By changing which atoms receive particular energy shifts, scientists can tune the system to produce a variety of entangled states without altering the physical hardware.

“You turn these lasers on and wait, and at some point the system stabilizes into an interesting, highly entangled quantum state,” said Anjun Chu, a postdoctoral researcher in the Clerk group and first author of the new work. “By simply adjusting the lasers, we can access kinds of entangled states that no one had thought about before.”

Building Better Quantum Sensors

One of the most promising uses for the new approach is quantum sensing.

In theory, entangled quantum states can detect extremely small differences in magnetic fields or gravitational fields between separate locations. However, developing states that are both highly sensitive and resistant to noise has remained a major challenge.

The researchers demonstrated that a version of their proposed system containing two groups of atoms could be used to measure field gradients. When the two atomic ensembles are placed in different locations, the resulting quantum state reflects the difference between the local magnetic or gravitational fields. At the same time, it naturally rejects background noise that affects both locations equally.

“You’re able to do two things that are normally not compatible with one another: Use entanglement to build an exquisitely sensitive sensor but also have robustness to arbitrarily large amounts of noise,” Clerk said. “Normally, entanglement is very fragile. This approach has some amazing resilience.”

Another advantage is that the information stored in these quantum states can be extracted using standard Ramsey measurement techniques, eliminating the need for specialized or exotic measurement methods.

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What if you aren’t actually in control of your own destiny? What if another version of you from some parallel universe is steering the wheel of your life? Or, what if an infinite number of alternate “yous” are all tugging at the controls simultaneously?

That’s essentially the argument physicist Vlatko Vedral laid out recently in Popular Mechanics, using quantum physics to dismantle the idea that human consciousness magically creates reality.

First, let’s start by defining the “observer effect,” because it’s the widely accepted idea that Vedral is smashing apart. The observer effect is the idea that simply observing or measuring something inevitably alters it. One classic example is a tire pressure gauge. By checking tire pressure, you’re allowing a small amount of air to escape; thus, by merely observing/measuring, you have altered the subject.

A Physicist Says Quantum Physics May Be Stranger Than the Observer Effect

According to Vedral, the observer effect has been badly mangled by decades of internet philosophy and stoner dorm-room interpretations of quantum mechanics. The simplified version says that particles exist in multiple states until someone observes them, causing reality to “collapse” into a single outcome.

The idea became so popular and widely accepted, largely for the wrong reasons, that it even trickled down into New Age spirituality, where people try to manifest wealth with positive vibes, assuming that they can pull the strings of the universe with their mere acknowledgment of said strings.

The observer effect is a very human-centric concept that may even seem a bit arrogant. It puts us front and center in the forces of the universe, assuming that our mere presence of a natural act is enough for these forces to change the way they work as if they were trying to impress us, like when your boss walks by, so you start working extra hard.

Vedral says that’s nonsense, and that observation is nothing special. Consciousness doesn’t bend reality. Interactions do. Any kind of interaction. A photon hitting sunglasses, an electron colliding with an atom, and light entering your eye are all definite events that will happen whether or not a human is paying attention.

Vedral stuck with the example of a photon hitting someone’s sunglasses to make his point. He argues that quantum mechanics states that two separate realities can exist at the same time: in one branch, a photon passes through the lens and reaches your eye, and in another, it is deflected away by the sunglasses. Both versions of “you” continue to march along separate quantum paths.

Vlatko Vedral is basically arguing that quantum physics doesn’t say humans magically create reality just by looking at things. Instead, reality is constantly changing us through every interaction we have with the world. You are changing because you have become part of one possible outcome rather than another.

Vedral then takes the idea even further, suggesting that all these alternate versions of reality still technically exist and may even influence one another under very specific conditions. In simple terms, there may be countless slightly different versions of you constantly being created by every tiny interaction you have with the world, most of which you’ll never notice.

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For decades, theoretical physicists tossed around the idea that time reflection, also known as “time mirrors,” might one day be demonstrated in a real-world experiment.

This idea seemed too big and wild, yet it kept popping up in serious discussions of quantum mechanics where equations hinted at surprising behavior.

A team led by Hady Moussa from the Advanced Science Research Center at the CUNY Graduate Center (CUNY ASRC) in New York City has now confirmed that these mysterious events actually exist.

They pulled off a successful test by changing the properties of a device in a quick, uniform way so that signals reversed direction in time.

Understanding time mirrors

This sort of time flip has been described as looking into a mirror and spotting your back instead of your face. It sounds like science fiction, but it has a basis in real physics.

Researchers had predicted for more than 50 years that sudden shifts in a wave’s environment could trigger such reversals.

Time reflections differ from everyday mirror views in one crucial way. Instead of light or sound bouncing back in space, the wave is forced to reverse its flow in time.

That shift causes the frequency of the wave to change, sparking a chain reaction of interesting phenomena in the system.

In normal reflections, you see an immediate image or hear an echo. A time reflection, on the other hand, makes part of the signal run backward.

There is no need for any speculation about time travel, though, since these effects involve a swift flip in the medium’s physical traits.

Time mirrors and metamaterials

To achieve this, the group used an engineered metamaterial designed to control electromagnetic wave behavior in unusual ways. Metamaterials allow scientists to manipulate waves far beyond ordinary mirrors or lenses.

By carefully adjusting electronic components on a strip of metal, they introduced a sudden jump that reversed the direction of incoming signals. They filled the strip with electronic switches hooked to capacitor banks.

That arrangement supplied the necessary burst of energy to force the wave to flip direction in time, an effect that used to be considered nearly impossible with accessible power.

The outcome was a time-reversed copy of the original wave, appearing just as predicted but never before seen with clarity.

Adjusting the system’s impedance at the right instant was key. Impedance is a measure of how much a structure resists electric current, and doubling it turned out to be the trick for flipping the wave in time.

By pulling this off in a lab setting, they proved that the energy hurdle can be overcome when conditions are precisely controlled.

Past attempts had failed because uniform shifts across the entire device were tough to generate, but the new approach surmounted that barrier.

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