Session B1: New Directions in Quantum Control of AMO Systems

Developments in the Coherent Control of Collisional Processes

Experimental and theoretical studies of the Coherent Control of unimolecular processes has seen spectacular growth over the last two decades. By contrast, Coherent Control of collisional processes remains a significant challenge. We describe: (1) the entanglement requirement for fixed energy scattering that makes controlled collisional experiments difficult, (2) demonstrate a viable theoretical proposal for control of collision induced ionization, and (3) introduce a time dependent approach that provides a new direction that bypasses entanglement requirements for collisional control. Applications to attosecond scenarios are computationally examined and shown to provide excellent control in the particular cases examined.   

Coherent control of infinite-dimensional quantum systems

Theories of quantum control have hitherto made the assumption that the Hilbert space of a quantum system can be truncated to finite-dimensions. All the beautiful results of optimal control of chemical reactions, and control in quantum computing are based upon ths premise. Controllability in an infinite- dimensional quantum system is hard to prove with conventional methods, and infinite-dimensional systems provide unique challenges in designing control fields. In this talk, I will present recent dense-subspace controllability results for an infinite-dimensional quantum system. These results are important from the viewpoint of developing more efficient state-to-state transfer protocols, particularly in quantum computing. I will present examples from the control of infinite-dimensional quantum systems such as Rydberg atoms and trapped-ions. This work expands the scope of quantum control research to beyond that of finite-dimensional quantum systems.   

Frontiers in quantum feedback control

Feedback control of open quantum systems is an intriguing new topic for both fundamental and applied research. In this talk I will discuss our group's ongoing theoretical and experimental work in this area. Our current activity in measurement-feedback control focuses on the development of new methods for quantum precision measurement and sensing. In particular we are trying to understand the utility of feedback control methods in enabling novel quantum metrology protocols, and to elucidate corresponding performance-robustness-complexity tradeoffs. Coherent feedback is an emerging new paradigm for quantum control, in which scattered quantized fields are processed unitarily (without conversion into classical information) and then directed back into the system. We are just beginning a program of research on this topic, aimed at experimental validation of the basic theory.   

Fourier Synthesis and Robust Control of Quantum Dynamics

The problem of manipulating quantum systems with uncertainities or inhomogeneties in parameters governing the system dynamics is ubiquitous in spectroscopy, metrology and quantum information processing. Typical settings include resonance offsets, inhomogeneties in strength of excitation field, time dependent noise, adressing errors etc. There is widespread use of adiabatic and composite pulses to compensate for these inhomogeneties. In this talk we describe the mathematical aspects of quantum dynamics that make such compensation possible. We analyze what kind of errors can and cannot be corrected. Finally we describe Fourier synthesis methods for design of compensating pulse sequences. Applications of these ideas to NMR spectroscopy in inhomogeneous static and radio-frequency fields are discussed.