### Lecturer

Chancellor’s Fellow

Former Marie Skłodowska-Curie Fellow (project OPERACQC)

JA 7.14, Department of Physics,

University of Strathclyde,

107 Rottenrow

Glasgow, G4 0NG

U.K.

Telephone: +44 (0)141 548 4231

Fax: +44 141 552 2891

e-mail: marco.piani@nullstrath.ac.uk

### Personal Statement

I joined the University in 2014 as Lecturer and Chancellor’s Fellow. My research deals with Quantum Information Processing, and focuses principally on the quantum properties of correlations exhibited by distributed quantum systems. My goals are those of deepening our understanding of quantum mechanics and facilitating the development of revolutionary quantum technologies. The latter go from unconditionally secure communications to improved measurement devices, to the efficient simulation of quantum systems, to incomparably faster computers. I am also interested in outreach and public engagement, in the belief that these activities are essential for the scientific literacy of the general population and to secure the public support to scientific research itself.

### Research Interests

My research deals with **Quantum Information Processing** (**QIP**), and focuses principally on the quantum properties of correlations exhibited by distributed quantum systems.

The advent of Quantum Mechanics established a profound fracture in the way we describe and understand the world, revealing counterintuitive features of nature that still puzzle both the general public and the scientists. From a fundamental point of view, any aspect of quantum mechanics that cannot be accounted for in the realm of classical mechanics, that is, any sign of *quantumness*, is worth investigating in order to better understand quantum mechanics and nature itself. From a practical point of view, the history of science and technology – including, for example, the invention of the laser and the transistor — indicates that any quantum effect may be considered as having the potential to lead to disruptive technologies.

QIP is the result of the recognition that “*Information is physical*” (R. Landauer), combined with the fact that the basic laws of nature are quantum. This opens the opportunity to store and process information in ways that go beyond, for example, the standard — or, as typically referred to, classical — computers, based on a binary and exclusive logic. The extension of the theory of information and computation to the quantum case provides a number of promising applications, which range from a possible exponential speedup of quantum computers with respect to classical computers — e.g., in solving computational problems and efficiently simulating quantum systems — to secure cryptographic communication schemes. This has led to a huge effort, on both the theoretical and experimental sides, to “harness the quantum world”. At the core of the advantage of QIP over classical information processing lie quantum correlations, which are my main interest.

Quantum **entanglement** results when two or more quantum systems become so tightly intertwined that, in a sense, their shared properties dominate over their individual ones; for example, there can be at the same time perfect knowledge about a composite system and total uncertainty about its components. This can give rise to stronger-than-classical correlations between quantum systems, and indeed entanglement was already considered the most prominent quantum feature by one of the fathers of Quantum Mechanics, Erwin Shroedinger. Entanglement has proven to be a key resource in many QIP tasks; it allows, for example, quantum teleportation and quantum cryptography. It is then clear that the study of entanglement is both of practical and fundamental importance. The recent years have seen a growing interest in entanglement theory and many experiments nowadays aim at the generation, manipulation and use of entanglement. However, entanglement is not the whole story as, for example, quantum correlations need to be accessed and exploited by performing measurements. Based on the interplay between quantum states and local quantum measurements, the quantumness of correlations can thus assume stronger forms, like *steering* and *nonlocality*, for which entanglement is necessary but not sufficient, or weaker forms, like quantum *discord*, for which entanglement is sufficient but not necessary. Indeed, correlations can have quantum features even in the absence of entanglement, a fact recently linked to a potential quantum advantage in a number of QIP tasks even in the presence of a high level of noise.

In the above context, one may cast the relation between the foundational and applicative issues regarding quantum behavior in the following way:

*Taking optimal advantage of quantum behavior requires the best possible understanding of it*.

At the core of my research activity, which lies at the intersection of Mathematics, Physics and Information Theory, are the objectives of characterizing and exploiting the quantum properties of single and distributed systems. While I have often focused on the detection, generation and manipulation of entanglement, in the course of my career I have become more broadly interested in those physical effects that manifest the quantum features of nature. The unifying idea is that non-classicality is a very general property of single and multipartite systems, that goes beyond entanglement; at the same time entanglement is an extreme form of non-classicality that allows otherwise impossible effects, and as such it deserves special focus.

### Recent publications

M. Piani, “Channel steering”, arXiv:1411.0397 (2014), submitted to J. Opt. Soc. Am. B

M. Piani and J. Watrous, “Necessary and Sufficient Quantum Information Characterization of Einstein-Podolsky-Rosen Steering”, Phys. Rev. Lett. 114, 060404 (2014), arXiv:1406.0530 (2014) pdf

F. G. S. L. Brandao, M. Piani, and P. Horodecki, “Quantum Darwinism is Generic”, arXiv:1310.8640 (2013)

M. Piani, V. Narasimhachar, and J. Calsamiglia, “Quantumness of correlations, quantumness of ensembles and quantum data hiding”, New J. Phys. 16, 113001 (2014), arXiv:1405.1640

L. Chen, O. Gittsovich, K. Modi, and M. Piani, “Role of correlations in the two-body-marginal problem”, Phys. Rev. A 90, 042314 (2014), arXiv:1310.1110