terahertz pulses in non-chiral crystals

Terahertz Pulses Create chirality in Non-Chiral Crystals

Understanding Chirality in Crystals

Chirality describes objects that cannot be perfectly aligned with their images, regardless of rotations or translations—similar to how left and right human hands differ. In chiral crystals, the atomic arrangement imparts a unique "handedness," affecting properties such as optical behavior and electrical conductivity.

Research Focus: Antiferro-Chiral Crystals

Characteristics of Antiferro-Chiral Crystals

A research collaboration between Hamburg and Oxford has studied antiferro-chiral crystals, a type of non-chiral structure analogous to antiferromagnetic materials, where magnetic moments anti-align in a staggered pattern, resulting in no net magnetization.

Composition of Antiferro-Chiral Crystals

These crystals contain equal proportions of left-and right-handed substructures within a unit cell, making them overall non-chiral.

Breakthrough: Inducing Chirality with Terahertz Light

Key Researchers and Their Approach

The research group, headed by Andrea Cavalleri from the Max-Planck Institute for the Structure and Dynamics of Matter, utilized terahertz light to disrupt the balance of the non-chiral material boron phosphate (BPO₄), thereby inducing finite chirality on an ultrafast timescale.

Published Findings

This research has been published in Science by the team.

Nonlinear Phononics: A Game-Changing Mechanism

Explanation of the Methodology

"As part of our approach, we utilize a concept known as  nonlinear phononics," say Zhiyang Zeng, lead author. "By stimulating a particular terahertz frequency vibrational mode, which displaces the crystal lattice along the axes of other modes, we were able to create a chiral state that lasts for several picoseconds," he further explains.

Selective Induction of Chirality

"Significantly by rotating the polarization of her terahertz light by 90 degrees, we were able to selectively induce either a left-or right-handed chiral structure," adds co-author Michael Forst.

Potential Applications and Future Prospects

"This discovery paves the way for dynamic control of matter at the atomic scale," says Cavalleri, group leader at the MPSD.

Advancing Technological Innovations

"We are eager to explore the potential applications of this technology and its capacity to create novel functionalities. The ability to induce chirality in non-chiral materials opens up possibilities for ultrafast memory devices and more advanced optoelectronic platforms."

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Study Shows Grapes Enhance Quantum Sensor Performance

Introduction: Quantum Technology and Grape-Powered Innovation

A team from Macquarie University has revealed that everyday supermarket grapes hold the potential to enhance quantum sensor capabilities, driving innovations in quantum technology.

Research Highlights: Grapes and Microwave Magnetic Field Hotspots

Research published in Physical Review Applied on 20 December 2024 highlights how grape pairs produce concentrated microwave magnetic field hotspots, paving the way for smaller, cost-effective quantum devices.

The Role of Magnetic Fields in Quantum Sensing

Previous Studies Focused on Electric Fields

Lead author Ali Fawaz, a quantum physics Ph.D. candidate at Macquarie University, stated, "While prior research emphasized the role of electrical fields in the plasma effect, our study highlights how grape pairs can strengthen magnetic fields critical to quantum sensing."

Inspiration from Popular Culture: Grapes and Plasma Formation

This research is inspired by popular social media videos showcasing the formation of plasma—glowing electrically charged particles—when grapes are microwaved.

Shifting Focus: Magnetic Field Effects in Quantum Research

While earlier research emphasized electric fields, the Macquarie team investigated magnetic field effects, which are vital for quantum applications.

Using Nano-Diamonds for Quantum Sensing

The team utilized nano-diamonds featuring nitrogen-vacancy centers, atomic-scale defects that serve as quantum sensors, capable of detecting magnetic fields by mimicking the behavior of tiny magnets.

The Role of Defect Centers in Quantum Sensing

Dr. Sarath Raman Nair, co-author of the study and lecturer in quantum technology at Macquarie University, stated. "Pure diamonds lack color, but replacing carbon atoms with certain other atoms produces 'detect' centers with optical characteristics."

The Role of Nitrogen-Vacancy Centers for Quantum Sensing

"In this research, the nitrogen-vacancy centers within the nanodiamonds function as tiny magnets, making them ideal for quantum sensing purposes."

Experimental Setup: Quantum Sensor Between Grapes

The researchers mounted their quantum sensor—a diamond embedded with special atoms—on the end of slender glass fiber, positioning it between two grapes. By directing green laser light through the fiber, they induced a red glow from the atoms, with the brightness of the glow indicating the strength of the surrounding microwave field.

Magnetic Field Strength Increased by Grapes

"Through this technique, we observed that the magnetic field of the microwave radiation doubles in strength when the grapes are added," says Fawaz.

Implications for Quantum Technology Miniaturization

Opportunities for Compact and Efficient Devices

Professor Thomas Volz, senior author and leader of the Quantum Materials and Applications Group at Macquarie's School of Mathematical and Physical Sciences, states that these findings open up exciting opportunities for the miniaturization of quantum technology.

Future of Quantum Devices: Compact and Efficient Designs

"This study paves the way for investigating alternative microwave resonator designs for quantum technologies, which could result in more compact and efficient quantum sensing devices," he says.

The Im portance of Grape Size and Shape in Quantum Sensing

The size and shape of the grapes were vital to the success of the experiment. The team's work depended on grapes of exact dimensions—each around 27 millimeters long—to focus microwave energy at the optimal frequency for the diamond quantum sensor.

Water vs. Sapphire: Grapes and Quantum Sensing

Quantum sensing devices have typically relied on sapphire for this function. However, the Macquarie team proposed that water could perform even better. This made grapes, which consist mostly of water encased in a thin skin, ideal for testing their hypothesis.

Challenges in Harnessing Water's Microwave Concentrating Power

"Water is more effective than sapphire at concentrating microwave energy, yet it is less stable and dissipates more energy during the process. This is the primary challenge we need to address," says Fawaz.

Looking Beyond Grapes: Developing New Materials for Quantum Sensing

Expanding beyond grapes, the researchers are now working on developing more dependable materials that can harness water's unique properties, moving us closer to creating more efficient sensing devices.

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Physics Experiment Reveals Order in Quantum Chaos

Breakthrough Discovery in Quantum Research

UC Santa Cruz physicist Jairo Velasco, Jr., and a global team of researchers have confirmed the existence of order within chaos in the quantum domain. Their findings, published in Nature on November 27, verify a 40-year-old theory that electrons confined to quantum space adhere to predictable trajectories rather than displaying chaotic behavior.

The Nature of Electrons: Particle and Wave Characteristics

Electrons demonstrate both particle and wave-like characteristics, defying simple behavior such as rolling like a ball. Their counterintuitive nature becomes evident as their wave properties, under specific conditions, interact to form concentrated movement patterns. Physicists refer to these shared trajectories as "unique closed orbits."

The Role of Graphene in Quantum Experiments

In Velasco's lab, achieving this breakthrough necessitated an elaborate blend of sophisticated imaging techniques and meticulous control of electron behavior within graphene. This material, renowned for its unique properties and two-dimensional nature, is frequently used in research to observe quantum phenomena.

Using Advanced Imaging Techniques to Study Electron Movement

Velasco's team employed the sharp-tipped probe of a scanning tunneling microscope in their experiment to initially create an electron trap and then positioned it near a graphene surface to observe electron movements without causing physical disruption.

Implications for Electronics: Efficient Electron Movement

According to Velasco, one major advantage of electrons following closed orbits within a confined space is that their intrinsic properties are better maintained as they move between points. This could have significant implications for electronics, as information encoded in electron properties could be transferred without loss, potentially leading to low-power, highly efficient transistors.

"One of the most exciting possibilities of this discovery lies in its use for information processing." Velasco explained. "With slight disturbances, or 'nudges' to these orbits, electrons could travel in a predictable manner across a device, conveying information from one side to the other."

Video

[A numerical simulation depicting the quantum dynamics achieved in the team's experiment. Credit: Anton Graf, Harvard University.]

Understanding Quantum Scars: The Imprint of Electron Trajectories

The Origins of Quantum Scarring

In the field of physics, these distinct electron trajectories are referred to as "quantum scars." This concept was first introduced in a 1984 theoretical study by Eric Heller, a physicist at Harvard University, who used computer simulations to demonstrate that electrons confined in a space would trace high-density paths due to the constructive interference of their wave motions.

"Quantum scarring is more than just an intriguing phenomenon; it provides insight into the peculiar nature of the quantum realm," said Heller, who also co-authored the paper. "Scarring represents a form of localization around orbits that retrace their paths. In the classical world, such returns have no lasting impact and are quickly forgotten. However, in the quantum world, they are perpetually retained."

Potential Applications of Quantum Scars in Technology

With Heller's theory now validated, researchers have the empirical basis to investigate practical applications. Current transistors, already operating at the nanoelectronic level, could achieve greater efficiency through quantum scar-based designs, potentially improving devices such as computers, smartphones, and tablets that depend on compact, high-performance transistors to enhance processing ca pabilities.

"Looking ahead, we aim to expand our work on visualizing quantum scars to create techniques for controlling and manipulating scar states," said Velasco. "Harnessing chaotic quantum phenomena could lead to new, precise methods for the selective and adaptable delivery of electrons at the nanoscale, opening the door to innovative quantum control approaches."

A Comparative Analysis of Classical and Quantum Chaos

Visualizing Chaos: The 'Billiard' Model

Velasco's team uses a visual representation known as a 'billiard' to demonstrate the classical mechanics of linear and chaotic systems. This model involves a confined area that shows the movement of particles, with the 'stadium' shape being a common example characterized by curved ends and straight sides. In the realm of classical chaos, particles exhibit erratic, unpredictable motion, eventually covering the entire area.

Observing Quantum Chaos in Action

The experiment involved creating a stadium billiard on atom-thin graphene, measuring approximately 400 nanometers in length. With the aid of a scanning tunneling microscope, the team successfully observed quantum chaos, revealing the intricate pattern of electron orbits within the stadium billiard built in Velasco's lab.

"I'm thrilled that we managed to capture images of quantum scars in an actual quantum system," said Zhehao Ge, a UC Santa Cruz graduate student and first co-corresponding author of the study. "We hope that these findings will contribute to a more profound understanding of chaotic quantum systems."

Acknowledgments and Collaborations

The paper, titled "Direct Visualization of Relativistic Quantum Scars in Graphene Quantum Dots," includes co-authors:

• UC Santa Cruz: Peter Polizogopoulos, Ryan Van Haren, and David Lederman
• Harvard University: Anton Graf and Joonas Keski-Rahkonen
• University of Manchester: Sergey Slizovskiy and Vladimir Fal'ko
• Japan's National Institute for Materials Science: Takashi Taniguchi and Kenji Watanabe

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Achieving Universal Control in Quantum Dot Systems with Four Singlet-Triplet Qubits

Introduction to Quantum Dot-Based Quantum Systems

Precise manipulation of interacting spins in quantum systems is central to developing reliable, high-performing quantum computers, but remains a significant challenge in nanoscale systems with numerous quantum-dot-based spins.

Breakthrough from TU Delft: Universal Control of Four Singlet-Triplet Qubits

A team from Delft University of Technology (TU Delft) recently demonstrated universal control of a quantum-dot-based system with four singlet-triplet qubits, as reported in Nature Nanotechnology, potentially advancing scalable quantum information processing.

Lieven Vandersypen's Insight

According to Lieven Vandersypen, the study's senior author, "Our initial aim was to fine-tune and calibrate the exchange interactions among neighboring spins within a 4x2 quantum dot arrya, each loaded with a single spin," he shared with Phys.org.

"Using time-domain measurements, we eventually realized that we had effectively attained universal control over four singlet-triplet qubits, which are joint states of two spins. We then focused extensively on benchmarking the quantum operations accurately and generating entanglement throughout the qubit array."

Key Innovation: Extending Universal Control to Four Qubits

Before this research, systems with universal control were restricted to a maximum of two singlet-triplet qubits. Vandersypen and his colleagues broke new ground by achieving this control in a quantum dot-based system with four singlet-triplet qubits.

Spin Control and Quantum Operations

"Each qubit in our configuration is made up of two spins, with single-qubit operations controlled by baseband voltage pulses," Vandersypen described."These pulses adjust the spin-spin exchange interaction to alternate between two values, aligning with two distinct qubit rotation axes. For two-qubit gates, we apply gate voltage pulses to activate exchange coupling between spins on separate qubits."

Building the Quantum Dot System

Quantum Dot Ladder Structure

The researchers built a system with a 2x4 germanium quantum dot array, creating a quantum dot ladder. Through controlled exchange interactions between spin pairs along the rungs, they first determined the qubit energy spectrum of the system.

Achieving Universal Control and SWAP-Style Gates

The researchers achieved universal control of individual qubits by pulsing both detuning and tunneling barriers in each double quantum dot. By coordinating this control across neighboring qubits, they ultimately developed a SWAP-style quantum gate to transfer information between qubit pairs.

Key Results and Future Directions

Vandersypen explained, "In this device, all eight spins are involved in the quantum coherent time evolution, marking the hightest number achieved in semiconductor quantum dot arrays to date. Our results also underscore the potential of the singlet-triplet qubit. While the single-qubit operations are already highly reliable, with a fidelity exceeding 99%, the next essential step is to demonstrate that the two-qubit gate can be performed with a fidelity above 99%."

Next Steps in Quantum Control

Vandersypen and his team's recent work presents an innovative approach for achieving universal control over germanium quantum dot-based systems with four singlet-triplet qubits. Looking ahead, this technique could be refined to allow for the precise manipulation of even larger nanoscale quantum systems.

Implications for Future Quantum Technologies

The ability to precisely control these systems could enable physicists to consistently simulate intricate physical phenomena, such as quantum magnetism. Furthermore, it may contribute to the advancement of more sophisticated quantum information systems.

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Revolutionizing Timekeeping: Quantum Physics Enhances Optical Atomic Clock Precision Through Entanglement

Introduction to Quantum clocks

Envision entering a room adorned with grandfather clocks, each ticking at its own distinct rhythm. Quantum physicists at the University of Colorado Boulder and the National Institute of Standards and Technology (NIST) have replicated this concept at the atomic scale. Their breakthrough could lead to the development of innovative optical atomic clocks, which measure time through the inherent 'ticking' of atoms.

Advancements in Clock Technology

Lattice of Strontium Atoms

The team's new clock consists of a lattice of several dozen strontium atoms. To enhance the clock's accuracy, they introduced quantum entanglement between groups of atoms, effectively combining four distinct clocks into one time-keeping system.

Surpassing the Quantum Limit

This is no ordinary pocket watch: The researchers demonstrated that, under specific conditions, their clock surpassed the standard quantum limit for precision--what physicist Adam Kaufman describes as the 'Holy Grail' for optical atomic clocks.

"By dividing the same interval into increasingly smaller units, we are achieving higher precision in time measurement," said Kaufman, senior author of the study and fellow at JILA, a joint institute of CU Boulder and NIST. "This advancement could enable us to measure time with unprecedented accuracy."

The team's breakthroughs may pave the way for novel quantum technologies, including sensors capable of detecting minute environmental changes, such as variations in Earth's gravitational field with altitude.

Key Findings and Methodology

Creating an Optical Atomic Clock

Kaufman and his co-authors, including Alec Cao, JILA graduate student and first author, released their study on October 9 in Nature.

Lassoing Atoms

The findings represent a major leap for optical atomic clocks, which can perform functions far exceeding basic timekeeping.

To create such a device, scientists generally start by trapping and cooling a cluster of atoms to extremely low temperatures. A powerful laser is then applied to excite the atoms. When the laser is precisely tuned, the electrons orbiting the atoms transition between lower and higher energy states, repeatedly cycling. This process is akin to a grandfather clock's pendulum, except these clocks oscillate over a trillion times per second.

These clocks are, remarkably precise. For instance, the latest optical atomic clocks at JILA can measure changes in gravitational pull if they are lifted by as little as a fraction of a millimeter.

Addressing Uncertainty in Atomic Clocks

According to Kaufman, optical clocks serve as a crucial platform in various fields of quantum physics, as they enable precise control over individual atoms---regarding both their locations and their states.

However, they come with a significant limitation: In quantum physics, even atomic-scale entities often behave in unpredictable ways. These inherent uncertainties establish what appears to be an insurmountable limit on the precision of a clock.

The Role of Quantum Entanglement

Entanglement, however, might pave the way for a workaround. Kaufman described that when two particles enter an entangled state, knowledge about one particle inherently provides insights into the other. In practical terms, entangled atoms within a clock act less as distinct entities and more as a unified atom, resulting in more predictable behavior.

Cloud-Like Orbits:

In the present study, the researchers created this type of quantum connection by gently adjusting their strontium atoms, causing the electrons to orbit significantly away from the nuclei-resembling the appearance of cotton candy.

"Think of it as a cloud-like orbit," Kaufman noted. "This cloudiness means that when two atoms are sufficiently close, their electrons can detect one another, resulting in a powerful interaction."

These paired atoms oscillate at a rate that surpasses that of individual atoms.

Experimental Results

The team conducted experiments on clocks that integrated both single atoms and entangled groups of two, four, and eight atoms--effectively creating four clocks and distinct ticking rates within a single device.

They discovered that, under specific conditions, entangled atoms exhibit significantly less uncertainty in their oscillation compared to atoms in conventional optical atomic clocks.

"This means we can arrive at the same precision level in a shorter duration," he observed.

Future Potential and Challenges

Ongoing Research

Superior Command:

He and his team have considerable work ahead of them. Currently, the researchers can only operate their clock effectively for approximately 3 milliseconds; beyond this duration, the entanglement among atoms begins to degrade, leading to chaotic atomic ticking.

Implications for Quantum Computing

However, Kaufman recognizes significant potential in the device. His team's method of entangling atoms could serve as a foundation for what physicists refer to as "multi-qubit gates"--fundamental operations that enable calculations in quantum computers which may one day surpass traditional computers in specific tasks.

A Vision for the Future

Kaufman posed the question: "Is it possible to develop new types of clocks with customized properties, utilizing the precise control we have over these systems?"

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Groundbreaking Achievement in Quantum Computing: Inaugural Teleportation of Logical Qubits by Quantinuum

Introduction of the Quantum Leap

In a groundbreaking achievement, engineers and physicists at Quantinuum, a quantum computing company, have performed the inaugural teleportation of a logical qubit through fault-tolerant methods. The team's research, published in the journal Science, elaborates on the configuration and techniques utilized for teleportation, along with the fidelity metrics obtained.

Overcoming Challenges in Quantum Computing

The development of a truly functional quantum computer faces a major hurdle due to the propensity for errors during computational tasks. A viable method for minimizing these errors involves the use of logical qubits, which can be effectively distributed across several physical qubits.

Utilizing H2 Trapped-Ion Quantum Processor

In this innovation project, the research team engaged their H2 trapped-ion quantum processor, allowing for the transfer of quantum-encoded information using entangled physical qubits.

Advantages of Logical Qubits

Logical qubits are generally less error-prone than physical qubits because they are shielded from noise and can be encoded with error-correcting codes.

Exploring Teleportation Methods

The main hurdle in utilizing logical qubits involves teleporting information through quantum entanglement. In their pursuit of a solution, the researchers at Quantinuum examined two approaches: transversal and lattice surgery.

Transversal Approach

In the transversal approach, operations were applied to several qubits at once, enabling the manipulation of the process and thereby expediting teleportation.

Lattice Surgery Technique

In contrast, the lattice surgery technique focused on altering qubit boundaries to execute operations, which is advantageous for improving procedural compatibility across various architectures.

Comparison of Methods

The researchers found that both the transversal and lattice surgery methods were viable for the transportation of logical qubits; however, each method had its drawbacks. In particular, the lattice surgery approach exhibited less fidelity than the transversal technique.

Real-Time Decoding and Error Correction

In both scenarios, the research team employed real-time decoding via the Steane code to implement error correction at four distinct stages of the teleportation process, marking the first successful demonstration of logical qubit teleportation using fault-tolerant methods.

Conclusion: A Milestone in Quantum Computing

The achievements of the Quantinuum team mark a significant milestone in the ongoing pursuit of developing a genuine quantum computer.

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