The measurement of quantum nonlocal observables lies at the foundations of quantum theory. We report an implementation of the von Neumann instantaneous measurements of nonlocal observables which becomes possible due to technological achievements in creating hyperentangled photons. Tests of reliability and of the nondemolition property of the measurements have been performed with high precision...
Measurements are crucial in quantum mechanics, because of features like the wave function collapse after a “strong” (projective) measurement or the fact that measuring a quantum mechanical observable completely erases the information on its conjugate.
Nevertheless, quantum mechanics allows for different measurement paradigms including weak measurements (WMs), i.e. measurements performed with...
The Aharonov Albert Vaidman weak values provide a starting point for a time symmetric ontology to quantum mechanics. While some of the work on weak measurements hinted at such an ontology, it was never formally defined. I will provide results for the initial steps taken in formally defining a weak value ontology, starting with an operational definition for weak values. The operational...
A weak measurement performed on a pre- and post-selected quantum system can result in an average value that lies outside of the observable’s spectrum. This effect, usually referred to as an “anomalous weak value”, is generally believed to be possible only when a non-trivial post-selection is performed, i.e., when only a particular subset of the data is considered. In this work we show,...
Quantum statistics have a profound impact on the properties of systems composed of identical particles. At the most elementary level, Bose and Fermi quantum statistics differ in the exchange phase, either 0 or $\pi$, which the wave function acquires when two identical particles are exchanged. I will report on a scheme to directly probe the exchange phase with a pair of massive particles by...
The geometric phase can be characterized by the weak value. By considering weak measurement with decoherence, we can operationally define the geometric phase with decoherence. This definition can be connected to the Uhlmann's defined geometric phase for mixed states. Furthermore, the experimental demonstration is discussed in linear optics.
We present an implementation of a superadiabatic protocol proposed by Demirplack and Rice and by Sir Michael Berry in a superconducting circuit consisting of a transmon device operated as a qutrit (three-level system). The adiabatic process studied is STIRAP (stimulated Raman adiabatic passage), which in our system is realized by coupling the two transitions by Gaussian microwave pulsed with...
Recent experimental measurements of the transition path time distributions of proteins demonstrate that these distributions are experimentally measurable. The folding unfolding dynamics of proteins is classical mechanical in nature but the experiments motivated the development of a quantum theory of transition path time distributions [1-3]. The formalism was applied to define a tunneling...
Weak values (WV) and two-state-vector formalism (TSVF) [1] provide novel insights in quantum-information processing, quantum thermodynamics, nanoscale quantum systems, complex materials, etc.
In the theoretical part of the talk, we explore a new quantum effect of scattering accompanying an elementary collision of two quantum systems A and B, the latter interacting with a quantum ...
Where do classical and quantum mechanics part ways? How do classical and quantum randomness fundamentally differ? Here we derive (nonrelativistic) quantum mechanics and classical (statistical) mechanics within a common axiomatic framework. The common axioms include conservation of average energy and conservation of probability current. Two axioms distinguish quantum from classical...
Electron microscopy has revolutionized our understanding of biomolecules, cells, and biomaterials, by enabling their analysis through imaging with (near-) atomic-scale resolution. However, the high-energy electrons typically used for electron microscopy are known to cause damage to biological specimens. Specimen damage is related to the fact that image information is shot-noise limited,...
We will briefly review possibilities of experiments exploring quantum aspects of the electron field interaction using structured electron beam.
Among these we can mention the vertical version of the Aharonov Bohm effect and the light electron coupling through Landau states.
Moreover we will illustrate the use of the orbital angular momentum (OAM) sorter and electrostatic elements in order to...
TBA
A customary relativistic quantum scattering theory implies that all the particles in a reaction have definite momenta, that is, they are described by the delocalized plane waves. When the well-normalized wave packets are used instead (say, of Gaussian form), the scattering cross sections get corrections of the order of $\lambda_c^2/\sigma_{\perp}^2 \ll 1$ where $\lambda_c$ is a Compton wave...
The laws of thermodynamics classify energy changes for macroscopic systems as work performed by an external driving and heat exchanged with the environment. For quantum systems in contact with an external environment, the very identification of heat and work is a challenge, since work cannot be directly accessed by measurement. Quantum systems continuously monitored by a detector have recently...
Fractional quantum Hall states are predicted to host exotic anyonic excitations, which offer the exciting prospect of topologically-protected quantum computation. Mach-Zehnder interferometry has been suggested as a probe for the anyonic statistics. However, all experimental attempts to measure such an interference signal have failed to date, despite the high visibility of interference fringes...
In the macroscopic limit, quantum mechanics reproduces the deterministic laws of motion associated with classical physics. Nevertheless it is impossible to reconcile the uncertainty limited statistics of quantum dynamics with the classical notion of causality as expressed by universal laws of motion. Here, I explain how the complex phases of Hilbert space describe a causality dominated by the...
Linear physics is "easy" to solve. Whether in a purely quantum mechanical system, or when considering quantum fields, quadratic (i.e., linear) Hamiltonians give rise to well known and established phenomena. Exotic and trademark phenomena in quantum field theory in curved spacetime, such as the Hawking effect and the Unruh effect, are all consequences of linear physics.
Most physics is, in...
We propose a theoretical scheme in which a regularized scalar field theory emerges naturally from entangling an otherwise standard scalar field with an ancillary, non-dynamic field. Using suitable initial and final Gaussian states of the two-field system, it is possible to retain the Feynman-diagrammatic expansion of the standard theory with a modified ‘’weak” propagator having a regularized...
We consider a two-player coordination game, similar in spirit to the
CHSH game, in which Alice and Bob attempt to maximize the area of a
rectangle. Alice and Bob each have two random variables, and the
rectangle’s area is represented by a certain parameter, which is a
function of the correlations between their random variables. We show
that this parameter is a Bell parameter - i.e., the...
We point out a fundamental problem that hinders the
quantization of general relativity: quantum mechanics is formulated in
terms of systems, typically limited in space but infinitely extended
in time, while general relativity is formulated in terms of events,
limited both in space and in time. Many of the problems faced while
connecting the two theories stem from the difficulty in...
The uncertainty associated with the probing of quantum state is expressed in terms of the effective abundance (measure) of possibilities for its collapse. New kind of uncertainty limits entailed by quantum description of the physical system arise in this manner.
Most thermodynamic systems live and die by the Boltzmann exponential;
the standard occupation functions (Fermi-Dirac, Bose-Einstein, and
Boltzmann) are defined by it. In discrete energy systems, state
degeneracy is usually of secondary importance, while in continuous energy
systems, density of states functions may dominate the Boltzmann factor at
low energies but never at high. However,...
Holographic duality shows increasing evidence of a deep relation between quantum entanglement in quantum field theory (QFT) and gravity. While the 'entanglement entropy' captures spacetime physics outside a black hole horizon, the 'complexity' is proposed to be dual to the inside of the horizon. Contrary to much progress on the 'holographic complexity', complexity in QFT is not defined well....
This talk will present our recent efforts towards quantifications and unification of quantum macroscopicity, coherence, and nonclassicality. It will first cover our size measure for macroscopic quantum superpositions based on the phase-space structure [1] and another measure based on the degree of disturbance by coarse-grained measurements [2]. We will then present a more recent result that...
We propose the idea that time evolution of quantum systems is driven by work. The formalism presented here falls within the scope of a recently proposed theory of gravitating quantum matter where extractible work, and not energy, is responsible for gravitation. Our main assumption is that extractible work, and not the Hamiltonian, dictates dynamics. We find that expectation values of...
During eighties of last century, Horodecki proposed Three Wave Hypothesis (TWH). This hypothesis is based on
• the Paris school interpretation of quantum mechanics, which is related to de Broglie’s particle-wave duality, Vigier’s and others’ works, and
• the assumption of covariant æther.
TWH implies that a massive particle is an intrinsically spatially as well as temporally extended...
Improving the precision of measurements is a significant challenge for the scientific community. Quantum metrology provides ways to overcome the standard quantum limit (SQL) of 1/\sqrt{N} and to reach the fundamental Heisenberg limit (HL) of 1/N.It has been suggested that both quantum entanglement and nonlinear interactions are important resources for quantum metrology, which can result in a...
The introduction and promotion by Aharonov, Vaidman, and others of weak values (WVs) connected to weak measurements and postselection has opened a new, fruitful subfield of quantum mechanics (QM). As all new endeavors it has also met with some criticism. In my contribution, I will look at some of these critical issues: How is the WV of a projector to be interpreted? Does the strength of the...
