STIR: Many-body localized quantum information processing in AMO systems
Abstract
The coherent control and manipulation of complex quantum systems is one of the central challenges in modern atomic, molecular and optical physics. The majority of ongoing research in this direction focuses on building up this complexity starting from individual, isolated degrees of freedom. In contrast, the opposite approach, where one seeks the coherent local manipulation of a strongly interacting system is generally thought to be intractable. The main difficulty, of course, is the exponentially growing Hilbert space with a typical many-body eigenstate strongly coupled to an exponentially dense set of other states. We propose to explore an alternate approach toward the coherent control of many-body "qubits", following a new paradigm introduced by recent studies of strongly interacting, disordered quantum systems. In particular, we propose to investigate a novel architecture for quantum information processing based upon the many-body localized phase. In thermal phases, the quantum coherence of individual degrees of freedom is rapidly lost to the environment. By contrast, many-body localized (MBL) phases limit the spread of this coherence and appear promising for quantum information applications. In particular, the slow-growth of entanglement in the MBL phase implies a relatively long intrinsic dephasing time-scale. Thus, quantum information stored in such many-body localized states could be extremely robust to decoherence. In addition to information storage, we propose to explore many-body localization as a new method to protect the transport and manipulation of quantum information. Together, the faithful storage and transmission of quantum information is the basic building block for applications ranging from information processing to communication and metrology. In a traditional architecture, quantum bits connect via channels that coherently shuttle information between remote nodes. Constructing such a channel from an interacting many-body system at high temperature is generally considered impossible; once quantum information disperses into the system, it rapidly decoheres due to scattering with thermal excitations. To avoid this, typical quantum channels, such as mechanical resonators, optical photons, superconducting strip-lines, and spin chains, are either specially tailored few-body systems or operate at ultra-low temperatures in order to freeze out parasitic degrees of freedom. Many-body localization offers an alternate strategy where such parasitic degrees of freedom are locally confined via disorder and thus, cannot cause decoherence. On the flip-side, to better characterize the failure of thermalizing quantum systems as platforms for information processing, we will explore the rate of scrambling in such systems. Scrambling refers to the process by which a localized bit of quantum information becomes entangled and hidden within complex many-body correlations under time evolution. The information in such a ÒscrambledÓ state has not been lost, since the final state is unitarily related to the initial state, but most of the information about the initial state is inaccessible to any reasonable local measurement. By understanding the nature and rate of scrambling in conventional many-body systems, it may be possible to identify alternate strategies to slow such dynamics, including the using of near-critical phases.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 31, 2018
- Source ID
- W911NF1710606
Entities
People
- Norman Y Yao
Organizations
- Army Contracting Command
- United States Army
- University of California, Berkeley