Nelly Huei Ying Ng

Bio: Nelly Huei Ying Ng is an academic researcher from Free University of Berlin. The author has contributed to research in topics: Quantum thermodynamics & Work (thermodynamics). The author has an hindex of 13, co-authored 26 publications receiving 1162 citations. Previous affiliations of Nelly Huei Ying Ng include Nanyang Technological University & Delft University of Technology.

The second laws of quantum thermodynamics

Abstract: The second law of thermodynamics places constraints on state transformations. It applies to systems composed of many particles, however, we are seeing that one can formulate laws of thermodynamics when only a small number of particles are interacting with a heat bath. Is there a second law of thermodynamics in this regime? Here, we find that for processes which are approximately cyclic, the second law for microscopic systems takes on a different form compared to the macroscopic scale, imposing not just one constraint on state transformations, but an entire family of constraints. We find a family of free energies which generalize the traditional one, and show that they can never increase. The ordinary second law relates to one of these, with the remainder imposing additional constraints on thermodynamic transitions. We find three regimes which determine which family of second laws govern state transitions, depending on how cyclic the process is. In one regime one can cause an apparent violation of the usual second law, through a process of embezzling work from a large system which remains arbitrarily close to its original state. These second laws are relevant for small systems, and also apply to individual macroscopic systems interacting via long-range interactions. By making precise the definition of thermal operations, the laws of thermodynamics are unified in this framework, with the first law defining the class of operations, the zeroth law emerging as an equivalence relation between thermal states, and the remaining laws being monotonicity of our generalized free energies.

Limits to catalysis in quantum thermodynamics

Abstract: Quantum thermodynamics is a research field that aims at fleshing out the ultimate limits of thermodynamic processes in the deep quantum regime. A complete picture of thermodynamical processes naturally allows for auxiliary systems dubbed 'catalysts', i.e., any physical systems facilitating state transformations while remaining essentially intact in their state, like an auxiliary system, a clock, or an actual catalyst. In this work, we present a comprehensive analysis of the power and limitation of such thermal catalysis. Specifically, we provide a family of optimal catalysts that can be returned with minimal trace distance error after facilitating a state transformation process. To incorporate the genuine physical role of a catalyst, we identify very significant restrictions on arbitrary state transformations under dimension or mean energy bounds, using methods of convex relaxations. We discuss the implication of these findings on possible thermodynamic state transformations in the quantum regime.

Maximization of Extractable Randomness in a Quantum Random-Number Generator

Abstract: Quantum random-number generators (QRNGs) play a decisive role in protocols for encrypted communication. Unfortunately, classical noise often spoils both the integrity and speed of such quantum devices. The authors demonstrate a new framework to harness maximum randomness without compromising security, and which allows for more cost-effective and smaller units. This work paves the way toward a reliable, high-bit-rate, and environmentally immune QRNG for information-security applications.

Experimental implementation of bit commitment in the noisy-storage model

Abstract: In quantum communication, the noisy-storage model assumes that an attacker’s memory device is imperfect, thus enabling two parties to implement protocols securely. Using polarization-entangled photon pairs, Ng et al. analyse and verify a two-party bit commitment protocol within the noisy-storage.

An experimental implementation of oblivious transfer in the noisy storage model.

Abstract: The oblivious transfer protocol is a cryptographic primitive used to create many different secure two-party schemes. Here, Erven et al. provide the first implementation of the oblivious transfer protocol using entangled photons, within the noisy storage model.

Quantum internet: A vision for the road ahead

Abstract: The internet-a vast network that enables simultaneous long-range classical communication-has had a revolutionary impact on our world. The vision of a quantum internet is to fundamentally enhance internet technology by enabling quantum communication between any two points on Earth. Such a quantum internet may operate in parallel to the internet that we have today and connect quantum processors in order to achieve capabilities that are provably impossible by using only classical means. Here, we propose stages of development toward a full-blown quantum internet and highlight experimental and theoretical progress needed to attain them.

Quantum resource theories

Abstract: This review introduces a new development in theoretical quantum physics, the ``resource-theoretic'' point of view. The approach aims to be closely linked to experiment, and to state exactly what result you can hope to achieve for what expenditure of effort in the laboratory. This development is an extension of the principles of thermodynamics to quantum problems; but there are resources that would never have been considered previously in thermodynamics, such as shared knowledge of a frame of reference. Many additional examples and new quantifications of resources are provided.