In Print

A collection of my most cited research papers, and a selection of my books.

My Research

Witnessing superpositions of causal orders by weak measurements at a given time

The questions we raise in this letter are as follows: What is the most general representation of a quantum state at a single time? Can we adapt the current representations to the scenarios in which the order of quantum operations are coherently or incoherently superposed? If so, what is the relation between the state at a given time and the uncertainty in the order of events before and after it? By establishing the relationship of two-state vector formalism with pseudo-density operators, we introduce the notion of single-time pseudo-state which can be constructed by either ideal or weak measurements. We show…

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Interference in quantum field theory: detecting ghosts with phases

We discuss the implications of the principle of locality for interference in quantum field theory. As an example, we consider the interaction of two charges via a mediating quantum field and the resulting interference pattern, in the Lorenz gauge. Using the Heisenberg picture, we propose that detecting relative phases or entanglement between two charges in an interference experiment is equivalent to accessing empirically the gauge degrees of freedom associated with the so-called ghost (scalar) modes of the field in the Lorenz gauge. These results imply that ghost modes are measurable and hence physically relevant, contrary to what is usually thought….

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A New Look at the C⁰-formulation of the Strong Cosmic Censorship Conjecture

We examine the C0-formulation of the strong cosmic censorship conjecture (SCC) from a quantum complexity-theoretic perspective and argue that for generic black hole parameters as initial conditions for the Einstein equations, corresponding to the expected geometry of a hyperbolic black hole, the metric is C0-extendable to a larger Lorentzian manifold across the Cauchy horizon. To demonstrate the pathologies associated with a hypothetical validity of the C0 SCC, we prove it violates the “complexity=volume” conjecture for a low-temperature hyperbolic AdSd+1 black hole dual to a CFT living on a (d−1)-dimensional hyperboloid Hd−1, where in order to preserve the gauge/gravity duality we…

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Are There Any Real Problems With Quantum Gravity?

We present a short, general and accessible introduction to quantizing gravity in the Heisenberg picture. We then apply this formalism to the scenario where two spatially superposed masses interact through the gravitational field. We discuss some of the consequences for quantum gravity including the spin of the graviton, the notions of locality and causality, as well as going beyond the linear regime. We use the Schwinger action principle and the Heisenberg representation which we believe make the issues involved clearer. We conclude by commenting on a number of traditionally discussed apparent problems with quantizing gravity (only to, ultimately, deny their…

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Classical Evolution Without Evolution

The well known argument of Page and Wootters demonstrates how to “derive” the usual quantum dynamics of a subsystem in a global state which is an eigenstate of the total Hamiltonian. I show how the same argument can be made in classical physics, by using a formalism that closely resembles the quantum one. This is not surprising since the Hamilton-Jacobi formulation of classical dynamics is precisely motivated by the logic of timeless dynamics. Ultimately, the key to obtaining dynamics without dynamics is the principle of energy conservation which leads to correlations between times pertaining to different subsystems. The same can,…

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Amplification of Gravitationally Induced Entanglement

Observation of gravitationally induced entanglement between two massive particles is the evidence of quantum nature of gravity. However, quantum effects in the gravitational field are exceptionally small so that the existing quantum-gravity proposals are extremely hard to test in practice. For addressing this key challenge, here we propose a criterion based on the logical contradictions of weak entanglement, which may boost the sensitivity of the signal due to the gravitationally induced entanglement. Specifically, we make use of the weak-value scenario and Einstein-Podolsky-Rosen (EPR) steering. We prove that it is impossible for a classical mediator to act on two local quantum…

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My Books

My Blog

Substack

Entropic Forces

This mysteriously sounding concept is widely used in biology. The chief reason being that life, in fact, is a struggle against the Second Law of thermodynamics.

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Crazy Quantum (Late-Night) Thoughts

The main obstacle to us making progress in quantum physics is the persistent (and misplaced) belief that quantum physics needs to be fixed.

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What is a Q-Field?

I have frequently talked about the interpretation of quantum physics implying that “everything is a quantum wave”. Here I’d like to explain this a bit better and, more importantly, tell you about some problems with this picture of the universe.

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Vlatko Vedral

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Musings on Quantum Mechanics

In Print