In Print

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

My Research

Planar Rotor in Matrix Mechanics and the Role of States in Quantum Physics

We illustrate Heisenberg’s method of matrix mechanics using the planar quantum rotor example. We show how to find the spectrum of this simple model without the need to use the eigenstates of the system. This then leads us to speculate on the role the Heisenberg state plays in quantum mechanics and to ask whether one could even completely dispose of the need for states.

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The Bose-Marletto-Vedral proposal in different frames of reference and the quantum nature of gravity

Observing spatial entanglement in the Bose-Marletto-Vedral (BMV) experiment would demonstrate the existence of non-classical properties of the gravitational field. We show that the special relativistic invariance of the linear regime of general relativity implies that all the components of the gravitational potential must be non-classical. This is simply necessary in order to describe the BMV entanglement consistently across different inertial frames of reference. On the other hand, we show that the entanglement in accelerated frames could differ from that in stationary frames.

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Witnessing superpositions of causal orders before the process is completed

The questions we raise in this letter are as follows: What is the most general representation of a quantum state at a single point in time? Can we adapt the current formalisms to situations where the order of quantum operations is coherently or incoherently superposed? If so, what are the relations between the state at a given time and the uncertainty in the order of events before and after it? Establishing the relationship between two-state vector formalism and pseudo-density operators, we introduce the notion of a single-time pseudo-state. The tomographic construction of single-time pseudo-states is possible by ideal or weak…

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Quantum Causal Inference with Extremely Light Touch

We consider the quantum version of inferring the causal relation between events. There has been recent progress towards identifying minimal interventions and observations needed. We here give an explicit quantum causal inference scheme using quantum observations alone for the case of a bipartite quantum system with measurements at two times. In this scenario there may be combinations of temporal and spatial correlations. We derive a closed-form expression for the space-time pseudo-density matrix associated with many times and qubits. This matrix can be determined by coarse-grained quantum observations alone and the protocol is in that sense extremely light touch. We prove…

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Matrix Mechanics of a Particle in a One-Dimensional Infinite Square Well

We solve the infinite potential well problem using the methods of Heisenberg’s matrix mechanics. In addition to being of educational value, the matrix mechanics allows us to deal with various unphysical issues caused by this potential in a seemingly unproblematic fashion. We also show how to treat many particles within this representation.

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Locality in the Schroedinger Picture of Quantum Mechanics

We explain how the so-called Einstein locality is to be understood in the Schrödinger picture of quantum mechanics. This notion is perfectly compatible with the Bell non-locality exhibited by entangled states. Contrary to some beliefs that quantum mechanics is incomplete, it is, in fact, its overcompleteness as exemplified by different pictures of quantum physics, that points to the same underlying reality.

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Visit the full research archive at Arxiv

My Books

Modern Foundations Of Quantum Optics
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Introductory Quantum Physics And Relativity
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Solid State Quantum Information
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Introduction to Quantum Information Science
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Decoding Reality
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From Micro to Macro
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My Blog

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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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If you'd like to ask me a question or discuss my research then please get in touch.

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