# It from Qubit: Principal Investigators

### Patrick Hayden

#### Collaboration Director

Patrick Hayden is a professor of physics at Stanford University. Prior to joining Stanford, Hayden was the Canada Research Chair in the Physics of Information at McGill University. He is currently a Simons Investigator, distinguished research chair of the Perimeter Institute for Theoretical Physics, and senior fellow of the Canadian Institute for Advanced Research.

Hayden’s research focuses on understanding the ultimate limits physics imposes on information processing, and finding ways to exploit quantum mechanics to achieve otherwise impossible communications and computing goals. Recently he has also been applying the methods of quantum information theory to the study of black hole physics and quantum gravity.

### Matthew Headrick

#### Collaboration Deputy Director

Matthew Headrick is an associate professor of physics at Brandeis University, where he has been since 2008. He received his Ph.D. from Harvard University and did postdoctoral work at the Tata Institute for Fundamental Research, Massachusetts Institute of Technology and Stanford.

Headrick’s work focuses on entanglement in quantum field theories, especially holographic ones. He has notably contributed to gathering evidence for holographic entanglement entropy formulas and to understanding their implications for holography and quantum gravity.

### Scott Aaronson

Scott Aaronson is an associate professor of electrical engineering and computer science at Massachusetts Institute of Technology. He studied at Cornell and University of California, Berkeley, and did postdocs at the Institute for Advanced Study as well as the University of Waterloo. His first book, *Quantum Computing Since Democritus*, was published in 2013 by Cambridge University Press. Aaronson has written about quantum computing for *Scientific American* and the *New York Times*, and writes a popular blog. He’s received the National Science Foundation’s Alan T. Waterman Award, the United States PECASE Award, and MIT’s Junior Bose Award for Excellence in Teaching.

Aaronson’s research focuses on the capabilities and limits of quantum computers and more generally on computational complexity and its relationship to physics. Within the context of the It from Qubit Collaboration, Aaronson is extremely interested in the interplay between computational complexity and quantum gravity. This has involved studying the computer-science aspects of the Harlow-Hayden argument, which attempts to apply complexity theory to the notorious “firewall paradox” in black hole information, as well as working with Leonard Susskind to understand the growth of quantum circuit complexity in systems arising from the AdS/CFT correspondence.

### Dorit Aharonov

Hebrew University

### Vijay Balasubramanian

Vijay Balasubramanian is a theoretical physicist at the University of Pennsylvania, where he holds a chair as the Cathy and Marc Lasry Professor. After completing his Ph.D. in physics at Princeton, Balasubramanian became a Junior Fellow of the Harvard Society of Fellows and for part of that time was also a Fellow-at-Large of the Santa Fe Institute. He spent the 2012/13 year at the École Normale Superieure in Paris, where he was the recipient of fellowship from the Fondation Pierre Gilles de Gennes. He has been a visiting professor at the CUNY Graduate Center, Rockefeller University and the Vrije Universiteit Brussel (Free University of Brussels), and a research associate at the International Center for Theoretical Physics (ICTP) in Trieste. He has received the Ira H. Abrams Memorial Award for Distinguishing Teaching, which is the highest teaching award given by the University of Pennsylvania’s School of Arts and Sciences.

Balasubramanian’s research in particle physics and string theory has related to the origin of the thermodynamics of gravitating systems, the apparent loss of quantum information in the presence of black holes and the structure of space-time. Using methods from statistical inference and information theory, he also investigates problems in the physics of living systems.

### Horacio Casini

Horacio Casini is an independent researcher for the National Scientific and Technical Council (CONICET), Argentina, and assistant professor at Instituto Balseiro, Bariloche, Argentina. He was awarded jointly, with Marina Huerta, Shinsei Ryu, and Tadashi Takayanagi, the New Horizons in Physics Prize in 2014 for “fundamental ideas about entropy in quantum field theory and quantum gravity.”

Casini’s research in the last 10 years has focused on entanglement entropy in quantum field theory, holography and gravity. In particular, he showed Bekenstein’s entropy bound coming from black hole physics is related to positivity of relative entropy and to distinguishability of states. In collaboration with Marina Huerta, he proved renormalization group irreversibility in three dimensions (called the F-theorem) from properties of entanglement entropy for circular regions.

### Juan Maldacena

Juan Maldacena is currently a professor at the Institute for Advanced Study in Princeton. He has worked on string theory and discovered a connection between quantum gravity and ordinary quantum mechanical systems, the so-called gauge/gravity duality. He has worked on many areas of theoretical physics, including quantum aspects of black holes, gauge theories and cosmological perturbation theory. He is a member of the National Academy of Sciences and of the American Academy of Arts and Sciences. He received the Dannie Heineman Prize in Mathematical Physics of the APS, the Dirac medal of the ICTP and the Breakthrough Prize in Fundamental Physics.

Maldacena has been interested in the connections between space-time and entanglement. He wants to understand in what sense entanglement “builds” space-time. Entanglement seems to be a crucial element, but there are probably other key ideas that are necessary to have a local space-time. One such element is a maximal amount of chaos in the basic dynamics of the fundamental degrees of freedom. Such chaos arises naturally in strongly interacting systems. He is currently studying some simple condensed-matter-inspired models that are strongly chaotic.

### Alexander Maloney

Alexander Maloney received his Ph.D. from Harvard University, which was followed by postdoctoral work at the Stanford Linear Accelerator Center and the Institute for Advanced Study. He moved to McGill University in 2007, where he is currently an associate professor and William Dawson Scholar.

Maloney’s work focuses on problems in quantum gravity and, in particular, on problems related to black hole quantum mechanics and the AdS/CFT correspondence. In the past, he has worked on simple models of quantum gravity, such as three-dimensional gravity, where it is possible to perform exact quantum mechanical computations that are impossible in more complicated theories.

### Donald Marolf

Don Marolf is a professor of physics at the University of California, Santa Barbara. He was an associate professor at Syracuse University until 2003. Marolf obtained his Ph.D. from the University of Texas at Austin in 1992. His awards include an NSF CAREER Award and fellowship in both the American Physical Society and the International Society for General Relativity and Gravitation.

Marolf’s research focuses on classical and quantum gravity, especially as related to black holes and gauge/gravity duality. Primary goals involve resolving the black hole information problem and better understanding the holographic bulk/boundary dictionary. The latter includes studies of holographic entropy as well as characterizations of gauge theory states dual to exotic bulk wormholes having either multiple boundaries or complicated internal topology.

### Robert Myers

Robert Myers is one of the founding faculty members at the Perimeter Institute for Theoretical Physics, where he is currently chair of the faculty. He is also an adjunct professor in the Department of Physics and Astronomy at the University of Waterloo. Myers has received a number of honors, including the 2012 CAP-TRIUMF Vogt Medal, the 2005 CAP-CRM Prize in Theoretical and Mathematical Physics and election to the Royal Society of Canada in 2006.

Myers is an expert on gravity and string theory with a large number of influential works on D-branes, black holes, and the AdS/CFT correspondence. In recent years, his research has focused on understanding the connection between entanglement entropy and space-time geometry.

### Jonathan Oppenheim

Jonathan Oppenheim is a professor of quantum theory in the Department of Physics and Astronomy (Quantum Information Group) at University College London (UCL). He currently holds a Royal Society Wolfson Merit Award and an EPSRC Established Career Fellowship. He completed his Ph.D. under Bill Unruh at the University of British Columbia in 2001 and was a postdoc under Don Page at the University of Alberta and Jacob Bekenstein at the Hebrew University of Jerusalem. In 2003, he moved to the University of Cambridge, where he held a Royal Society University Research Fellow. In 2012, he moved to UCL to take up his current position.

Oppenheim’s recent research focused on the field of quantum thermodynamics, which has very recently seen exciting progress inspired by ideas from quantum information theory. He also is active in the fields of quantum gravity, black hole thermodynamics, and the foundations of statistical mechanics. Although these fields are often distinct, there are many conceptual overlaps. His contributions include the discovery of new second laws of thermodynamics that become important at the quantum scale, and the discovery of negative information and quantum state merging. He is currently applying results from quantum information theory to understand black hole thermodynamics and quantum gravity. He is particularly interested in the black hole information paradox and holographic entanglement, and attempts to understand gravity from a thermodynamical perspective.

### Joseph Polchinski

Joe Polchinski is the Yzurdiaga Professor of Theoretical Physics at the University of California, Santa Barbara, and a permanent member of the Kavli Institute for Theoretical Physics (KITP). He obtained his Ph.D. from University of California, Berkeley, in 1980. After postdocs at SLAC and Harvard, he was at the University of Texas at Austin from 1984 to 1992, before moving to the KITP. Polchinski is a fellow of the American Physical Society, a member of the American Academy of Arts and Sciences, a member of the National Academy of Sciences and a fellow of the American Association for the Advancement of Science. He has been awarded the Dannie Heineman Prize in Mathematical Physics of the APS, the Dirac Medal of the ICTP, and the 2013 and 2014 Physics Frontiers Prize.

Polchinski works broadly in theoretical physics, including quantum field theory, string theory and gravity. His research is largely centered on the search for a theory of quantum gravity, building on the principle of AdS/CFT duality and on thought experiments such as the black hole information paradox. The firewall argument has revealed limits in our understanding and suggested many new directions. A key question is whether the framework of quantum mechanics needs to be modified in gravity. His current work focuses on connections among holography, quantum error correction, entanglement and quantum chaos.

### John Preskill

John Preskill is the Richard P. Feynman Professor of Theoretical Physics at the California Institute of Technology, and Director of the Institute for Quantum Information and Matter at Caltech. Preskill received his Ph.D. in physics in 1980 from Harvard. He was a Junior Fellow in the Harvard Society of Fellows and Associate Professor of Physics at Harvard before joining the Caltech faculty in 1983; he became the John D. MacArthur Professor in 2002, and the Richard P. Feynman Professor in 2010. Preskill is a member of the National Academy of Sciences, a fellow of the American Physical Society, and a two-time recipient of the Associated Students of Caltech Teaching Award. He has mentored more than 50 Ph.D. students and more than 45 postdoctoral scholars at Caltech, many of whom are now leaders in their research areas.

Preskill’s background is in particle physics and quantum field theory, but in the 1990s he got excited about the possibility of solving otherwise intractable problems by exploiting quantum physics. He has proposed potential applications of quantum computers to quantum simulation and other hard problems, and has developed methods for protecting quantum systems from decoherence using cleverly designed software and hardware. He is especially intrigued by the ways our deepening understanding of quantum information and quantum computing can be applied to other fundamental issues of physics, such as the classification of topological phases of matter, nonequilibrium quantum dynamics, the quantum properties of black holes, and the quantum structure of spacetime.

### Leonard Susskind

Stanford University

### Tadashi Takayanagi

Tadashi Takayanagi is a professor at Yukawa Institute for Theoretical Physics, Kyoto University. After he completed his Ph.D. in Tokyo University in 2002, he worked for four years as a postdoc at Harvard and KITP. He was an assistant professor at Kyoto University and an associate professor in Kavli IPMU, Tokyo University, before he moved to his current position in 2012. He has been awarded the Yukawa-Kimura Prize in 2011, the Nishinomiya-Yukawa Memorial Prize in 2013 and the New Horizons in Physics Prize in 2014.

Takayanagi’s main research contributions have been studies of quantum entanglement by using holography and quantum field theories. In particular, he discovered a holographic formula for entanglement entropy in 2006 with Shinsei Ryu. The main goals of his research are to reconstruct gravity and string theory as a theory of quantum entanglement and to understand dynamical properties of quantum entanglement in quantum field theories.

### Mark Van Raamsdonk

Mark Van Raamsdonk is a professor of physics at the University of British Columbia, where he also received his bachelor’s degree in mathematics and physics. He completed a Ph.D. in physics at Princeton University followed by postdoctoral research at Stanford University. Van Raamsdonk was a Canada Research Chair and Sloan Foundation Fellow and is currently a Simons Investigator. He was awarded the Canadian CAP/CRM Medal in Theoretical and Mathematical Physics in 2014.

Van Raamsdonk’s research focuses on understanding quantum gravity using the AdS/CFT correspondence in string theory. He is currently working to understand the implications for gravitational physics of fundamental results in quantum information theory, and also to understand better which properties of quantum states are required to describe gravitational space-times via the AdS/CFT correspondence.