Tag Archives: ultracold

Ultracold Atoms May Investigate Relativity in the Quantum Realm

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Spinning ultracold atoms could uncover the limits of Einstein’s relativity

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Small Ferris wheels made from light and extremely chilled particles could enable scientists to investigate elements of Albert Einstein’s theory of relativity on an extraordinary level.

Einstein’s special and general theories of relativity, established in the early 20th century, transformed our comprehension of time by illustrating that a moving clock can tick slower than a stationary one. If one moves rapidly or accelerates significantly, time measured will also increase. The same applies when an object moves in a circular path. While these effects have been noted in relatively large celestial entities, Vassilis Rembesis and his team at King Saud University in Saudi Arabia have developed a method to test these principles on a diminutive scale.

By examining rotation and time at the molecular level (atoms and molecules), they explored ultracold regions, just a few millionths of a degree above absolute zero. In this domain, the quantum behavior and movement of atoms and molecules can be meticulously controlled with laser beams and electromagnetic fields. In 2007, Rembesis and his colleagues formulated a technique to tune a laser beam to trap atoms in a cylindrical form, allowing them to spin. They refer to this as an “optical Ferris wheel,” and Rembesis asserts that their new findings propose that it can be used to observe relativistic time dilation in ultracold particles.

Their predictions indicate that nitrogen molecules are optimal candidates for investigating rotational time delays at the quantum level. By considering the movement of electrons within them as the ticks of an internal timer, the researchers detected frequency changes as minuscule as 1/10 quintillion.

Simultaneously, Rembesis noted that experiments utilizing optical Ferris wheels have been sparse up until now. This new proposal opens avenues for examining relativity theory in uncharted conditions where new or surprising phenomena may emerge. For instance, the quantum characteristics of ultracold particles may challenge the “clock hypothesis,” which states how a clock’s acceleration influences its ticking.

“It’s crucial to validate our interpretations of physical phenomena within nature. It’s often during unexpected occurrences that we need to reevaluate our understanding for a deeper insight into the universe. This research offers an alternative approach to examining relativistic systems, providing distinct advantages over traditional mechanical setups,” says Patrick Oberg from Heriot-Watt University, UK.

Relativistic phenomena, such as time dilation, generally necessitate exceedingly high velocities; however, optical Ferris wheels enable access to them without the need for impractically high speeds, he explains. Aidan Arnold from the University of Strathclyde, UK adds, “With the remarkable accuracy of atomic clocks, the time difference ‘experienced’ by the atoms in the Ferris wheel should be significant. Because the accelerated atoms remain in close proximity, there is ample opportunity to measure this difference,” he states.

By adjusting the focus of the laser beam, it may also become feasible to manipulate the dimensions of the Ferris wheel that confines the particles, allowing researchers to explore time-delay effects for various rotations, as noted by Rembesis. Nevertheless, technical challenges persist, including the need to ensure that atoms and molecules do not heat up and become uncontrollable during rotation.

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Source: www.newscientist.com

Ultracold Clock Sheds Light on Quantum Physics’ Impact on Time

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What is the quantum nature of time? We may be on the verge of discovering it

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How does time manifest for a genuine quantum entity? The most advanced clocks can rapidly address this query, enabling us to test various ways to manipulate and alter the quantum realm, thereby delving into the uncharted territories of physics.

The notion that time can shift originates from Albert Einstein’s special theory of relativity. As an object approaches the speed of light, it appears to experience time more slowly compared to a stationary observer. He expands upon this with a general theory of relativity, which demonstrates a similar temporal distortion in the presence of a gravitational field. Igor Pikovsky from the Stevens Institute in New Jersey and his team aim to uncover whether a similar effect occurs within the microscopic quantum landscape, utilizing ultra-cold clocks constructed from ions.

“The experiments we’ve performed until now have always focused on classical time, disregarding quantum mechanics,” says Pikovsky. “We’ve observed a regime where conventional explanations falter with an ion clock,” he continues.

These clocks consist of thousands of ions cooled to temperatures nearing absolute zero via laser manipulation. At such low temperatures, the quantum state of an ion and its embedded electrons can be precisely controlled through electromagnetic forces. Thus, the ticks of an ion clock are governed by the electrons oscillating between two distinct quantum states.

Since their behavior is dictated by quantum mechanics, these instruments provided an ideal platform for Pikovsky and his colleagues to investigate the interplay between relativistic and quantum phenomena on timekeeping. Pikovski mentions that they’ve identified several scenarios where this blending is evident.

One example arises from the intrinsic fluctuations inherent in quantum physics. Even at ultra-low temperatures, quantum objects cannot be completely static and instead must oscillate, randomly gaining or losing energy. Team calculations indicated that these fluctuations could lead to extended clock time measurements. Although the effect is minute, it is detectable in current ion clock experiments.

The researchers also mathematically analyzed the behavior of ions in a clock when “compressed,” resulting in “superpositions” of multiple quantum states. They found that these states are closely linked to the motion of the ions, influenced by their internal electrons. The states of ions and electrons are interconnected at a quantum level. “Typically, experiments necessitate creative methods to establish entanglements. The intriguing aspect here is that it arises organically,” explains team member Christian Sanner from Colorado State University.

Pikovski asserts that it is intuitive to think that quantum objects existing in superposition cannot simply perceive time linearly, though this effect has yet to be experimentally confirmed. He believes it should be achievable in the near future.

Team member Gabriel Solch from the Stevens Institute of Technology mentions that the next step is incorporating another crucial aspect of modern physics: gravity. Ultra-cold clocks can currently detect temporal extensions caused by significant variations in the Earth’s gravitational pull, such as when elevated by a few millimeters, but the exact integration of these effects with the intrinsic quantum characteristics of the clock remains an unresolved question.

“I believe it is quite feasible with our existing technology,” adds David Hume from the U.S. National Institute of Standards and Technology, Colorado. He highlights that the primary challenge is to mitigate ambient disturbances affecting the clock to ensure it doesn’t overshadow the effects suggested by Pikovsky’s team. Successful experiments could pave the way for exploring unprecedented physical phenomena.

“Such experiments are thrilling because they create a platform for theories to interact in a domain where they could yield fresh insights,” remarks Alexander Smith at St. Anselm College, New Hampshire.

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Source: www.newscientist.com

Revolutionary Quantum Funds Stored on Ultra-Cold ‘Debit Card’

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Quantum Debit Card Ensures Financial Security

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New quantum debit cards, which can hold unforgeable quantum funds, are constructed using extremely cooled atoms and light particles.

While standard banks often rely on the skill of counterfeiters to detect fake banknotes, quantum banks utilize the no-cloning theorem from physics, rendering counterfeiting impossible. This principle, which states that creating identical copies of quantum information is not feasible, led physicist Stephen Wiessner to propose a protocol in 1983 for generating secure currencies. Julian Laurat and his team at the Kastler Brossel Laboratory in France are actively implementing this groundbreaking concept in advanced experiments.

According to this protocol, banks create banknotes composed of quantum particles, possessing unique properties and existing in specific quantum states, thus ensuring protection against forgery through the no-cloning theorem. Laurat remarks that the protocol showcases an impressive feat of quantum cryptography, though it has not yet been put into practice for actual quantum fund storage.

The research team has made storage feasible by combining memory devices with hard drives. In their experiments, users interact with quantum systems that act as banks by exchanging photons. Each photon can be stored similarly to loading money onto a debit card.

The memory devices used by the team consist of hundreds of millions of cesium atoms, which researchers cool down to nearly absolute zero by bombarding them with lasers. At such extreme temperatures, light can precisely manipulate the quantum state of atoms, but Laurat notes that years were spent identifying the optimal cooling needed for atomic memory to serve as a quantum debit card. Through extensive testing, he and his colleagues demonstrated that users can retrieve photons from atoms without corrupting their states, as long as the process is not tampered with.

Christophe Simon from the University of Calgary emphasizes that the new experiment marks progress toward fully realizing quantum funding. However, the current quantum memory storage time of around six million seconds remains insufficient for practical application. “Another future step is to enhance portability. The long-term goal is to develop quantum memory that can be easily carried, particularly for Quantum Money applications. But we are not there yet,” he states.

The team is focused on extending storage durations, asserting that the protocol can be employed within quantum networks already being established in metropolitan areas across the globe. Additionally, cutting-edge quantum memory not only facilitates ultra-secure long-distance quantum communication but is also instrumental in connecting various quantum computers to more powerful systems.

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  • Quantum Computing/
  • Encryption

Source: www.newscientist.com

Ultra-Cold Atoms Defy Entropy and Resist Heating Up

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Some atoms simply refuse to follow entropy

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Repeated energization of vast collections of atoms should result in the disruption of their established structures, yet quantum effects appear to resist these changes.

The expected outcome for a physical system is “thermalization,” where everything becomes hot and eventually turns into a puddle of water. Intuitively, one might think that continuously throwing rocks at a sculpture would accelerate this process. Hanns-Christoph Negerl and his team at the University of Innsbruck in Germany conducted experiments that mimic this notion using some of the coldest atoms on Earth, but they observed no heating.

“We anticipated witnessing the opposite,” Negerl shares. The researchers utilized roughly 100,000 cesium atoms, cooling them down to billionths of absolute zero through laser and electromagnetic pulses. At this chilling temperature, atomic behavior becomes entirely quantum. They arranged the atoms in numerous single-layer tubes and employed additional laser pulses to “kick” them repeatedly.

These kicks were intended to provide the atoms with extra energy, which should have resulted in heating and varying speeds. However, team member Yanliang Guo reported that they observed no such changes, regardless of the kick intensity or the adjustments made to the interactions between atoms. The atoms continued to display remarkably similar speeds, behaving as if they were “frozen” within a singular quantum state.

The concept of quantum particles generating heat isn’t new, tracing back to the 1950s. The timing of such occurrences has long been a topic of debate among physicists. Team member Manuele Landini noted that while previous experiments revealed mechanisms for heating atoms, this current investigation may have unveiled novel physics by exploring an alternate range of parameters.

The mathematical framework explaining these phenomena is complex and often contradictory. Adam Ranson from the University of Lille in France commented that calculating whether interacting atoms will heat up is quite challenging, often resulting in researchers simplifying equations to two or three atoms. There exists a theory suggesting that the quantum states of highly interactive atoms can align in a manner that prevents energy absorption, but Ranson believes this picture remains incomplete.

Experiments like those conducted recently act as quantum simulators capable of deeper insights, although Rançon emphasized that further exploration of kick strengths and interactions is still needed.

Robert Connick at Brookhaven National Laboratory in New York has been developing mathematical models relevant to such experiments that project the unusual behavior of atoms. He posits that discovering systems resistant to energy absorption could inspire new developments in quantum technologies, offering a stable quantum state for long-term reliable detection or data storage. “Thermalization poses a significant threat to maintaining quantum effects,” he explains.

Researchers are already planning follow-up experiments to align atoms in thicker tubes, manipulate different tubes, and investigate the possibility of “freezing” their speeds.

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Source: www.newscientist.com