Physical interpretations of the time-symmetric formulation of quantum mechanics, due to Aharonov, Bergmann, and Lebowitz are discussed in terms of weak values. The most direct, yet somewhat naive, interpretation uses the time-symmetric formulation to assign eigenvalues to unmeasured observables of a system, which results in logical paradoxes, and no clear physical picture. A top–down ontological model is introduced that treats the weak values of observables as physically real during the time between pre-and post-selection (PPS), which avoids these paradoxes. The generally delocalized rank-1 projectors of a quantum system describe its fundamental ontological elements, and the highest-rank projectors corresponding to individual localized objects describe an emergent particle model, with unusual particles, whose masses and energies may be negative or imaginary. This retrocausal top–down model leads to an intuitive particle-based ontological picture, wherein weak measurements directly probe the properties of these exotic particles, which exist whether or not they are actually measured.

A long-standing challenge in the field of quantum physics is the efficient synchronization of individual and independently generated photons (i.e., light particles). Realizing this would have crucial implications for quantum information processing that relies on interactions between multiple photons.

Researchers at Weizmann Institute of Science recently demonstrated the synchronization of single, independently generated photons using an atomic quantum memory operating at room-temperature. Their paper, published in Physical Review Letters, could open new avenues for the study of multi-photon states and their use in quantum information processing.

“The project idea came about several years ago, when our group and the group of Ian Walmsley demonstrated an atomic quantum memory with an inverted atomic-level scheme compared to the typical memories—the ladder memory, named fast ladder memory (FLAME),” Omri Davidson, one of the researchers who carried out the study, told Phys.org. “These memories are fast and noise-free, and therefore they are useful for synchronization of single photons.”

An international team of scientists has succeeded in experimentally confirming a characteristic of topological materials.

Scientists from around the globe have experimentally confirmed a unique characteristic of topological materials. Using ‘3D glasses’-like technology and particle accelerators, they successfully visualized the relationship between an electron’s topology and its quantum mechanical properties, marking a significant step forward in understanding these future-focused materials.

Topological quantum materials are seen as a beacon of hope for energy-saving electronics and the high-tech of the future. A defining feature of these materials is their ability to conduct spin-polarized electrons on their surface, while remaining non-conductive inside. To put this into perspective: In spin-polarized electrons, the intrinsic angular momentum, i.e. the direction of rotation of the particles (spin), is not purely randomly aligned.

A laser for vibrational energy, rather than for light, operating in the quantum regime could teach researchers about the interplay between spin, vibration, and dissipation in quantum mechanics.

Phonon lasers replace the light excitations (photons) that are used in a standard laser with vibrational excitations of matter (phonons). Researchers have now coaxed two ions into forming a phonon laser containing fewer than 10 phonons, placing it firmly in the quantum regime [1], whereas previous phonon lasers had at least 10,000 phonons. The researchers plan to use this quantum phonon laser as a tool to investigate the role of dissipation in the behavior of quantum systems.

Dissipation—energy leaking into or out of a system in the form of heat—is often seen as a nuisance in physics, for example, when it takes the form of air resistance and reduces the fuel efficiency of a car or an airplane. But quantum systems also exhibit dissipation, and its effects in the quantum realm are not fully understood. Jonathan Home of the Swiss Federal Institute of Technology (ETH) in Zurich and his colleagues wanted to investigate how two separate sources of dissipation can interact to affect the behavior of a quantum system. “A laser is the simplest quantum system we could think of” that allows such experiments, Home says.