Lifeboat Foundation: Safeguarding Humanity
Toggle light / dark theme

Blog

Category: quantum physics – Page 118

Free-space optical communication links promise better security and increase bandwidths but can suffer from noise in daylight. This is particularly detrimental in quantum communications where current mitigation techniques, such as spectral, temporal, and spatial filtering, are not yet sufficient to make daylight tolerable for satellite quantum key distribution (SatQKD). As all current SatQKD systems are polarization-encoded, polarization filtering has not been investigated. However, by using time-and phase-encoded SatQKD, it is possible to filter in polarization in addition to existing domains. Scattered daylight can be more than 90% polarized in the visible band, yielding a reduction in detected daylight between 3 dB and 13 dB, such that polarization filtering can reduce the brightness of 780 nm daylight to below the unfiltered equivalent at 1,550 nm. Simulations indicate that polarization filtering increases the secure key rate and allows for SatQKD to be performed at dawn and dusk. This could open the way for daylight SatQKD utilizing shorter near-infrared wavelengths and retaining their benefits.

Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Read more | >

Physicists from the University of the Witwatersrand (Wits) have developed an innovative computing system using laser beams and everyday display technology, marking a significant leap forward in the quest for more powerful quantum computing solutions.

The breakthrough, achieved by researchers at the university’s Structured Light Lab, offers a simpler and more cost-effective approach to advanced quantum computing by harnessing the unique properties of light. This development could potentially speed up complex calculations in fields such as logistics, finance and artificial intelligence. The research was published in the journal APL Photonics as the editor’s pick.

“Traditional computers work like switchboards, processing information as simple yes or no decisions. Our approach uses to process multiple possibilities simultaneously, dramatically increasing computing power,” says Dr. Isaac Nape, the Optica Emerging Leader Chair in Optics at Wits.

Read more | >

Theoretical physicists have established a close connection between the two rapidly developing fields in theoretical physics, quantum information theory and non-invertible symmetries in particle and condensed matter theories, after proving that any non-invertible symmetry operation in theoretical physics is a quantum operation. The study was published in Physical Review Letters as an Editors’ Suggestion on November 6.

In physics, symmetry provides an important clue to the properties of a theory. For example, if the N-poles in a are replaced by the S-poles, and the S-poles by the N-poles all at once, the forces on objects and the energy stored in the magnetic field remain the same, even though the direction of the magnetic field has now become reversed. This is because the equations describing the magnetic field are symmetric with respect to the operation of swapping the N and S poles.

Over the past few years, the concept of symmetries has received generalization in various directions in the theoretical study of particle physics and condensed matter physics, becoming an active area of research. One such generalization is non-invertible symmetry. The operation of conventional symmetries is always invertible. There exists a reverse operation to undo it. Non-invertible symmetry, on the other hand, allows certain non-invertibility in such symmetry operations.

Read more | >

In the study of temporal mechanics, we have to venture beyond the confines of traditional objective science to incorporate the profound role of consciousness in shaping our understanding of time. The evidence and theories discussed throughout my upcoming paper (to be released as a Kindle eBook) suggest that the flow of time is not simply a physical phenomenon dictated by the laws of thermodynamics or the spacetime continuum, but rather a deeply psychological one, intertwined with consciousness itself. Time, as we experience it, emerges from our awareness of ongoing change—a continuous psychological construct that weaves our perceptions into a coherent narrative of past, present, and future.

The implications of this perspective are far-reaching. If the flow of time is indeed a function of consciousness, then time cannot be fully understood without accounting for the observer—the conscious entity whose perception of change gives rise to the experience of time. This challenges the classical notion of time as a separate, objective entity and places consciousness as a central player in the multidimensional matrix of reality.

Read more | >

Researchers have managed to coax a quantum computer to pulse with a rhythm unlike any before—a rhythm that defies conventional physics. For the first time, scientists have transformed a quantum processor into a robust time crystal, a bizarre state of matter that ticks endlessly without external energy.

This achievement, the work of physicists from China and the United States, could mark a turning point for quantum computing. By stabilizing the delicate systems that underpin this cutting-edge technology, the experiment hints at a path toward practical quantum computers capable of solving problems far beyond the reach of traditional machines.

Unlike conventional phases, such as solids or liquids, time crystals exist in a state of perpetual motion. Let me explain.

Read more | >

Quantum mechanics, a realm of the incredibly small, is often characterized by its paradoxical nature. One such paradox is the concept of superposition, where a quantum particle can exist in multiple states simultaneously. These delicate states, however, are notoriously fragile, often collapsing into a single, definite state within mere fractions of a second. Yet, a recent breakthrough has pushed the boundaries of quantum stability, achieving a record-breaking 23-minute lifespan for a specific type of superposition known as a cat state.

The term “cat state” is a whimsical reference to Schrödinger’s famous thought experiment, where a cat is placed in a box with a device that could randomly kill it. Until the box is opened, the cat is both alive and dead, a superposition of two states. In quantum mechanics, cat states manifest when a quantum object, such as an atom or a photon, exists in multiple states simultaneously, defying classical intuition.

While researchers have previously created cat states in laboratories, these states have been fleeting, quickly succumbing to the disruptive influence of their environment. However, a team led by Zheng-Tian Lu at the University of Science and Technology of China has managed to extend the lifespan of a cat state dramatically. They achieved this feat by manipulating a cloud of 10,000 ytterbium atoms, cooled to near absolute zero and trapped by laser light. By carefully controlling the atoms’ quantum states, the researchers were able to induce a superposition where each atom existed in two distinct spin states simultaneously.

Read more | >

Quantum computers operate using quantum gates, but the complexity and large number of these gates can diminish their efficiency. A new “hybrid” approach reduces this complexity by utilizing natural system interactions, making quantum algorithms easier to execute.

This innovation helps manage the inherent “noise” issues of current quantum systems, enhancing their practical use. The approach has been effectively demonstrated with Grover’s algorithm, enabling efficient searches of large datasets without extensive error correction.

Challenges of Quantum Computing.

Read more | >

In order to achieve the tunneling of atoms, the researchers used three optical tweezers and arranged them in a series. Then they introduced ultracold fermionic atoms (atoms that are cooled down to absolute zero temperatures) in this arrangement.

Using the three tweezers as traps, the researchers were able to control the tunneling rate of atoms by changing the distance between the traps. This approach allowed the researchers to successfully transfer atoms between the two outer tweezers.

“We observe a smooth and high-efficiency transfer of atoms between the two outer traps, with a very low population remaining in the central trap,” the researchers note in their study.

Read more | >