Lifeboat Foundation

Since it was first demonstrated in the 1960s, spontaneous parametric down-conversion (SPDC) has been at the center of many quantum optics experiments that test the fundamental laws of physics in quantum mechanics, and in applications like quantum simulation, quantum cryptography, and quantum metrology.

SPDC is the spontaneous splitting of a photon into two photons after it passes through a nonlinear object like certain crystals. The process is nonlinear and instantaneous, and the two output photons (called the signal photon and idler photon) satisfy conservation of energy and momentum compared to the input photon (the pump photon). SPDC is often used with a specially designed crystal to create pairs of entangled photons.

A research team from Canada has discovered that there is a delay between the detection of the two output photons, one that depends on the intensity of the incoming light that impacts the crystal. They call this a “gain-induced group delay.”

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.

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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 laser beams to process multiple possibilities simultaneously, dramatically increasing computing power,” says Dr. Isaac Nape, the Optica Emerging Leader Chair in Optics at Wits.

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 magnetic field 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.

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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.

Erbium and similar elements provide a wide range of electronic “handles” for manipulating atoms in many-body quantum experiments.

Combining quantum science with machine learning has led to a model that can accurately measure how surfaces feel to the touch.

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.

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.