[1] Time’s Arrow of a Quantum Superposition of Thermodynamic Evolutions. By G. Rubino , G. Manzano, and C. Brukner Fundamental laws of physics are generally time-symmetric. The directionality of time is then often explained with the thermodynamic arrow of time: the entropy of an isolated system increases during a process, and it is constant only …
The superpositions of thermodynamical arrows of time Read More »
Quantum gravity might soon be tested in the lab, thanks to a new analysis from our nodes in the UK, France and Hong Kong. Drawing on advances in quantum information science, the researchers have found that if gravity is fundamentally quantum rather than classical it must generate a signature known as non-Gaussianity. To look for …
PhysicsWorld: Quantum gravity could be tested using ultracold atoms Read More »
No quantum circuit can turn a completely unknown unitary gate into its coherently controlled version. Yet, coherent control of unknown gates has been realised in experiments, making use of a different type of initial resources. Here, we formalise the task achieved by these experiments, extending it to the control of arbitrary noisy channels, and to more general types of control involving higher dimensional control systems. For the standard notion of coherent control, we identify the information-theoretic resource for controlling an arbitrary quantum channel on a $d$-dimensional system: specifically, the resource is an extended quantum channel acting as the original channel on a $d$-dimensional sector of a $(d+1)$-dimensional system. Using this resource, arbitrary controlled channels can be built with a universal circuit architecture. We then extend the standard notion of control to more general notions, including control of multiple channels with possibly different input and output systems. Finally, we develop a theoretical framework, called supermaps on routed channels, which provides a compact representation of coherent control as an operation performed on the extended channels, and highlights the way the operation acts on different sectors.
The Quantum Information Structure of Spacetime (QISS) interdisciplinary initiative in Quantum Information and Quantum Gravity is announcing its first large conference, to be held at Western University, in London, Ontario, Canada, the week 6-11 June 2022. The main aim of the conference will be to foster dialogue between physics and philosophy. The conference will bring together …
Abstract: The invention of quantum theory in the 1920s represented a paradigm shift in our approach to describing the natural world. The focus on the object as a primitive shifted to the observation as a primitive. At the time, the first applications of interest came with a classical description in the language of Hamiltonian evolution, canonical variables and states. Staying close to this particular language lead to the development of the quantum formalism of Hilbert spaces, operators, Schrödinger equation and Born rule. Somewhat unfortunately, this standard formulation has come to dominate our understanding of what quantum theory is. While it was successfully employed in describing the micro-structure of matter and its relevant interactions, describing the dynamics of spacetime itself is outside of its scope. With the present talk I want to promote the idea that quantum theory is much more general than this standard formulation. I aim to clarify the essence of the paradigm shift that lies at the heart of the transition from classical to quantum theory. On this basis I then review the derivation from first principles of a more fundamental formulation of quantum theory, the positive formalism, and the recovery of the standard formulation as a special case.
A recent paper by Mucino, Okon and Sudarsky attempts an assessment of the Relational Interpretation of quantum mechanics. The paper presupposes assumptions that are precisely those questioned in the Relational Interpretation, thus undermining the value of the assessment.
QISS is supporting the Sejny Summer Institute organised by BRCP (Basic Research Community for Physics) For more information see sejny.sciencesconf.org
A New Scientist hosted lecture by Vlatko Vedral of the University of Oxford, where the audience has the opportunity to ask questions about quantum physics and the nature of reality. Further details here (EVENT HAD ENDED).
In this online event, Carlo Rovelli tells the extraordinary story of quantum physics and reveals its deep meaning: a world made of substances is replaced by a world made of relations, each particle responding to another in a never ending game of mirrors. Please see further details here (EVENT HAS ENDED).
Massive Klein-Gordon theory is quantized on the timelike hypercylinder in Minkowski space. Crucially, not only the propagating, but also the evanescent sector of phase space is included, laying in this way foundations for a quantum scattering theory of fields at finite distance. To achieve this, the novel $alpha$-K”ahler quantization scheme is employed in the framework of general boundary quantum field theory. A potential quantization ambiguity is fixed by stringent requirements, leading to a unitary radial evolution. Formulas for building scattering amplitudes and correlation functions are exhibited. A novel LSZ formula is derived, applicable to scattering at finite distance.
