Authors: Abraham Loeb (Harvard)
Does the collision of black hole singularities imprint an observable quantum signature on the resulting gravitational wave signal?
Authors: James B. Hartle (UCSB and SFI)
A brief remembrance of some aspects of the author’s scientific interaction with Stephen Hawking. A contribution to Physics Today’s March 14, 2018 web page in which Stephen Hawking is remembered by his colleagues.
Observables and unobservables in quantum mechanics: How the no-hidden-variables theorems support the Bohmian particle ontology
Author(s): M. Bahrami
Collapse models postulate that space is filled with a collapse noise field, inducing quantum Brownian motions, which are dominant during the measurement, thus causing collapse of the wave function. An important manifestation of the collapse noise field, if any, is thermal energy generation, thus dis…
[Phys. Rev. A 97, 052118] Published Fri May 18, 2018
Author(s): Ana Belén Sainz, Yelena Guryanova, Antonio Acín, and Miguel Navascués
To identify which principles characterize quantum correlations, it is essential to understand in which sense this set of correlations differs from that of almost-quantum correlations. We solve this problem by invoking the so-called no-restriction hypothesis, an explicit and natural axiom in many rec…
[Phys. Rev. Lett. 120, 200402] Published Fri May 18, 2018
Escape the thermal fate
Escape the thermal fate, Published online: 14 May 2018; doi:10.1038/s41567-018-0157-1
Many-body quantum systems fail to reach thermalization only under specific circumstances. An analysis now reveals a new, different kind of non-equilibrating dynamics based on the many-body analogue of quantum scars in single-particle quantum chaos.
Danko Georgiev and Eliahu Cohen
Phys. Rev. A 97, 052102 – Published 3 May 2018
Feynman’s sum-over-histories formulation of quantum mechanics has been considered a useful calculational tool in which virtual Feynman histories entering into a coherent quantum superposition cannot be individually measured. Here we show that sequential weak values, inferred by consecutive weak measurements of projectors, allow direct experimental probing of individual virtual Feynman histories, thereby revealing the exact nature of quantum interference of coherently superposed histories. Because the total sum of sequential weak values of multitime projection operators for a complete set of orthogonal quantum histories is unity, complete sets of weak values could be interpreted in agreement with the standard quantum mechanical picture. We also elucidate the relationship between sequential weak values of quantum histories with different coarse graining in time and establish the incompatibility of weak values for nonorthogonal quantum histories in history Hilbert space. Bridging theory and experiment, the presented results may enhance our understanding of both weak values and quantum histories.
- Scientific Reports volume 8, Article number: 7730 (2018)
Since its publication, Aharonov and Vaidman’s three-box paradox has undergone three major advances: i). A non-counterfactual scheme by the same authors in 2003 with strong rather than weak measurements for verifying the particle’s subtle presence in two boxes. ii) A realization of the latter by Okamoto and Takeuchi in 2016. iii) A dynamic version by Aharonov et al. in 2017, with disappearance and reappearance of the particle. We now combine these advances together. Using photonic quantum routers the particle acts like a quantum “shutter.” It is initially split between Boxes A, B and C, the latter located far away from the former two. The shutter particle’s whereabouts can then be followed by a probe photon, split in both space and time and reflected by the shutter in its varying locations. Measuring the former is expected to reveal the following time-evolution: The shutter particle was, with certainty, in boxes A+C at t1, then only in C at t2, and finally in B+C at t3. Another branch of the split probe photon can show that boxes A+B were empty at t2. A Bell-like theorem applied to this experiment challenges any alternative interpretation that avoids disappearance-reappearance in favor of local hidden variables.