M. Hamed Mohammady

M. Hamed Mohammady
Université Libre de Bruxelles | ULB · Centre for Quantum Information and Communication (QuIC)

Doctor of Philosophy

About

27
Publications
2,091
Reads
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382
Citations
Introduction
My current research interests lie at the intersection of thermodynamics and operational quantum physics. On the one hand, I wish to study how thermodynamic constraints impact the efficacy of quantum operations, most notably quantum measurements. On the other hand, I wish to establish a framework where the laws of thermodynamics, as they manifest themselves in the quantum regime, can be formulated in purely operational terms.
Additional affiliations
March 2019 - February 2021
Slovak Academy of Sciences
Position
  • MoRePro Postdoctoral Fellow
October 2017 - November 2018
Lancaster University
Position
  • Senior Researcher
April 2016 - August 2017
University of Exeter
Position
  • Research Fellow
Education
February 2009 - April 2013
University College London
Field of study
  • Theoretical Physics
October 2004 - August 2008
Imperial College London
Field of study
  • Physics

Publications

Publications (27)
Preprint
Full-text available
Measurement disturbance in the presence of conservation laws is analysed in general operational terms. We provide novel quantitative bounds demonstrating necessary conditions under which non-disturbance can be achieved, highlighting an interesting interplay between incompatibility, unsharpness, and coherence. As a by-product we obtain a substantial...
Preprint
Full-text available
Thermal channels -- the free processes allowed in the resource theory of quantum thermodynamics -- are generalised to thermal instruments, which we interpret as implementing thermodynamically free quantum measurements; a Maxwellian demon using such measurements never violates the second law of thermodynamics. The properties of thermal instruments a...
Article
Full-text available
Quantum measurement is ultimately a physical process, resulting from an interaction between the measured system and a measuring apparatus. Considering the physical process of measurement within a thermodynamic context naturally raises the following question: How can the work and heat be interpreted? In the present paper we model the measurement pro...
Article
Full-text available
Thermodynamic uncertainty relations express a trade-off between precision, defined as the noise-to-signal ratio of a generic current, and the amount of associated entropy production. These results have deep consequences for autonomous heat engines operating at steady state, imposing an upper bound for their efficiency in terms of the power yield an...
Article
Full-text available
In classical thermodynamic processes the unavoidable presence of irreversibility, quantified by the entropy production, carries two energetic footprints: the reduction of extractable work from the optimal, reversible case, and the generation of a surplus of heat that is irreversibly dissipated to the environment. Recently it has been shown that in...
Article
Full-text available
In thermodynamics, entropy production and work quantify irreversibility and the consumption of useful energy, respectively, when a system is driven out of equilibrium. For quantum systems, these quantities can be identified at the stochastic level by unravelling the system's evolution in terms of quantum jump trajectories. We here derive a general...
Article
Full-text available
A thermally isolated quantum system undergoes unitary evolution by interacting with an external work source. The two-point energy measurement (TPM) protocol defines the work exchanged between the system and the work source by performing ideal energy measurements on the system before and after the unitary evolution. However, the ideal energy measure...
Preprint
Quantum measurement is ultimately a physical process, resulting from an interaction between the measured system and a measuring apparatus. Considering the physical process of measurement within a thermodynamic context naturally raises the following question: How can the work and heat be interpreted? In the present paper we model the measurement pro...
Preprint
Full-text available
A thermally isolated quantum system undergoes unitary evolution by interacting with an external work source. The Two-Point energy Measurement (TPM) protocol defines the work exchanged between the system and the work source by performing ideal energy measurements on the system before, and after, the unitary evolution. However, the ideal energy measu...
Preprint
Full-text available
In thermodynamics, entropy production and work quantify irreversibility and the consumption of useful energy, respectively, when a system is driven out of equilibrium. For quantum systems, these quantities can be identified at the stochastic level by unravelling the system's evolution in terms of quantum jump trajectories. We here derive a general...
Preprint
Full-text available
Thermodynamic Uncertainty Relations express a trade-off between precision, defined as the noise-to-signal ratio of a generic current, and the amount of associated entropy production. These results have deep consequences for autonomous heat engines operating at steady-state, imposing an upper bound for their efficiency in terms of the power yield an...
Preprint
Full-text available
The increase in average energy of a quantum system undergoing projective energy measurements is referred to as "quantum heat", which is always zero. In the framework of quantum stochastic thermodynamics, this is constructed as the average over the fluctuating quantum heat (FQH), defined as the increase in expected value of the Hamiltonian along two...
Article
Full-text available
In this paper we introduce a definition for conditional energy changes due to general quantum measurements, as the change in the conditional energy evaluated before, and after, the measurement process. By imposing minimal physical requirements on these conditional energies, we show that the most general expression for the conditional energy after t...
Preprint
Full-text available
The unavoidable presence of irreversibility in classical thermodynamic processes carries two energetic footprints-the reduction of extractable work from the optimal, reversible case, and the generation of a surplus of heat that is irreversibly dissipated to the environment. Optimal thermodynamic protocols hence attempt to minimize irreversibility,...
Preprint
Full-text available
In this paper we investigate the relationship between the efficiency of a cyclic quantum heat engine with the Hilbert space dimension of the thermal baths. By means of a general inequality, we show that the Carnot efficiency can only be obtained when both the hot and cold baths are infinitely large. By further introducing a specific model where the...
Article
Full-text available
Conditional expectation values of quantum mechanical observables reflect unique non-classical correlations, and are generally sensitive to decoherence. We consider the circumstances under which such sensitivity to decoherence is removed, namely, when the measurement process is subjected to conservation laws. Specifically, we address systems with ad...
Preprint
Full-text available
Quantum open systems evolve according to completely positive, trace preserving maps acting on the density operator, which can equivalently be unraveled in term of so-called quantum trajectories. These stochastic sequences of pure states correspond to the actual dynamics of the quantum system during single realizations of an experiment in which the...
Chapter
Full-text available
Quantum open systems evolve according to completely positive, trace preserving maps acting on the density operator, which can equivalently be unraveled in term of so-called quantum trajectories. These stochastic sequences of pure states correspond to the actual dynamics of the quantum system during single realizations of an experiment in which the...
Article
Full-text available
We study a quantum Szilard engine that is not powered by heat drawn from a thermal reservoir, but rather by projective measurements. The engine is constituted of a system $\mathcal{S}$, a weight $\mathcal{W}$, and a Maxwell demon $\mathcal{D}$, and extracts work via measurement-assisted feedback control. By imposing natural constraints on the measu...
Article
Full-text available
We propose a general protocol for low-control refrigeration and thermometry of thermal qubits, which can be implemented using electronic spins in diamond. The refrigeration is implemented by a probe, consisting of a network of spins with two-body XXZ interactions. The protocol involves two operations: (i) free evolution of the probe; and (ii) a swa...
Article
Full-text available
Quantum state engineering and quantum computation rely on information erasure procedures that, up to some fidelity, prepare a quantum system in a pure state. Such processes occur within Landauer's framework if they rely on an interaction between the object and a thermal reservoir. Landauer's principle dictates that this must dissipate a minimum qua...
Thesis
Full-text available
A promising platform for quantum information processing is that of silicon impurities, where the quantum states are manipulated by magnetic resonance. Such systems, in abstraction, can be considered as a nucleus of arbitrary spin coupled to an electron of spin one-half via an isotropic hyperfine interaction. We therefore refer to them as "nuclear-e...
Article
Full-text available
Pulsed magnetic resonance allows the quantum state of electronic and nuclear spins to be controlled on the timescale of nanoseconds and microseconds respectively. The time required to flip dilute spins is orders of magnitude shorter than their coherence times, leading to several schemes for quantum information processing with spin qubits. Instead,...
Article
Full-text available
We present pulsed electron-nuclear double resonance (ENDOR) experiments which enable us to characterize the coupling between bismuth donor spin qubits in Si and the surrounding spin bath of 29Si impurities which provides the dominant decoherence mechanism (nuclear spin diffusion) at low temperatures (< 16 K). Decoupling from the spin bath is predic...
Article
Full-text available
We investigate electron paramagnetic resonance spectra of bismuth-doped silicon, at intermediate magnetic fields B≃0.1-0.6  T, theoretically and experimentally (with 9.7 GHz X-band spectra). We identify a previously unexplored regime of "cancellation resonances," where a component of the hyperfine coupling is resonant with the external field. We sh...
Article
Full-text available
There is growing interest in bismuth-doped silicon (Si:Bi) as an alternative to the well-studied proposals for silicon based quantum information processing (QIP) using phosphorus-doped silicon (Si:P). We focus here on the implications of its anomalously strong hyperfine coupling. In particular, we analyse in detail the regime where recent pulsed ma...

Projects

Project (1)
Project
To determine how the laws of thermodynamics, such as conservation of energy, restrict the kinds of quantum measurements that can be performed.