Direct optimization of signal-to-noise ratio of CPMG-like sequences in inhomogeneous fields

Mandal, Soumyajit; Borneman, Troy W.; Koroleva, Van D.M.; Hürlimann, Martin D.

doi:10.1016/j.jmr.2014.08.012

Cited by 15 publications

(4 citation statements)

References 36 publications

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“…The recent application of optimal control methods to the problem of heteronuclear decoupling yields not only significantly improved performance [377,378] but also unprecedented flexibility in the design of tailored decoupling sequences [379][380][381]. Individual pulses were also optimized for Carr-Purcell-Meiboom-Gill echo train sequences [382,383]. Beyond individually optimized pulses, the simultaneous optimization of pulses provides significant performance gains by exploiting cooperative effects either in a single scan [384] or in multiple scans [385] with first applications in Ramsey-type experiments and in Hahn echo sequences.…”

Section: State Of the Artmentioning

confidence: 99%

Training Schrödinger’s cat: quantum optimal control

et al. 2015

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Abstract. It is control that turns scientific knowledge into useful technology: in physics and engineering it provides a systematic way for driving a dynamical system from a given initial state into a desired target state with minimized expenditure of energy and resources. As one of the cornerstones for enabling quantum technologies, optimal quantum control keeps evolving and expanding into areas as diverse as quantumenhanced sensing, manipulation of single spins, photons, or atoms, optical spectroscopy, photochemistry, magnetic resonance (spectroscopy as well as medical imaging), quantum information processing and quantum simulation. In this communication, state-of-the-art quantum control techniques are reviewed and put into perspective by a consortium of experts in optimal control theory and applications to spectroscopy, imaging, as well as quantum dynamics of closed and open systems. We address key challenges and sketch a roadmap for future developments. ForewordThe authors of this paper represent the QUAINT consortium, a European Coordination Action on Optimal Control of Quantum Systems, funded by the European Commission Framework Programme 7, Future Emerging Technologies FET-OPEN programme and the Virtual Facility for Quantum Control (VF-QC). This consortium has considerable expertise in optimal control theory and its applications to quantum systems, both in existing areas, such as spectroscopy and imaging, and in emerging quantum technologies, such as quantum information processing, quantum communication, quantum simulation a e-mail: fwm@lusi.uni-sb.de and quantum sensing. The list of challenges for quantum control has been gathered by a broad poll of leading researchers across the communities of general and mathematical control theory, atomic, molecular-, and chemical physics, electron and nuclear magnetic resonance spectroscopy, as well as medical imaging, quantum information, communication and simulation. 144 experts in these fields have provided feedback and specific input on the state of the art, mid-term and long-term goals. Those have been summarized in this document, which can be viewed as a perspectives paper, providing a roadmap for the future development of quantum control. Because such an endeavour can hardly ever be complete (there are many additional areas of quantum control applications, such as spintronics, nano-optomechanical technologies etc.), this roadmap

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Section: State Of the Artmentioning

confidence: 99%

Training Schrödinger’s cat: quantum optimal control

et al. 2015

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“…To find sequences more robust towards field fluctuations, optimal control based algorithms [21][22][23] can be used to systematically search for refocusing cycles with modal structures that have no near degeneracies and associated low critical velocities for the range of offset frequencies of interest. This will eliminate nonadiabatic regions and result in a fully adiabatic spin dynamics.…”

Section: Measurements With Modified Refocusing Cyclesmentioning

confidence: 99%

Adiabatic and nonadiabatic behavior of the Carr-Purcell-Meiboom-Gill sequence in time-dependent magnetic fields

Hürlimann

Utsuzawa

Hou

2020

Phys. Rev. Research

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We investigate experimentally the effect of time-dependent magnetic fields on the spin dynamics of the Carr-Purcell-Meiboom-Gill sequence. The measurements demonstrate that the evolution is controlled by an effective Hamiltonian that is a function of the offset field and the sequence parameters. Over a wide range of offset fields, ramp rates, and sequence parameters, the system follows the effective Hamiltonian adiabatically. In this regime, the echo amplitudes exhibit characteristic modulations that reflect the changing directions of the eigenvector associated with the zero-energy level. The experimental results are in excellent quantitative agreement with theoretical predictions. Nonadiabatic events are observed at distinct offsets where the system becomes nearly degenerate. These nonadiabatic events occur precisely at the field offsets predicted by theory. After passing through such nonadiabatic regions, an abrupt change in the occupation of the zero-energy level is observed. In the adiabatic regime, the effects of field fluctuations are demonstrated to be fully reversible, while the occurrence of nonadiabatic events leads to hysteresis. The location and range of the adiabatic regions can be manipulated by modifying the pulse parameters.

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“…To find sequences more robust towards field fluctuations, optimal control based algorithms [16,15,17] can be used to systematically search for refocusing cycles with modal structures that have no near degeneracies and associated low critical velocites for the range of offset frequencies of interest. This will eliminate non-adiabatic regions and result in a fully adiabatic spin dynamics.…”

Section: Measurements With Modified Refocusing Cyclesmentioning

confidence: 99%

Observation of adiabatic and non-adiabatic behavior for CPMG sequence in time-dependent magnetic fields

Hürlimann,

Utsuzawa,

Hou

2020

Preprint

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We investigate experimentally the effect of time dependent magnetic fields on the spin dynamics of the Carr -Purcell -Meiboom -Gill (CPMG) sequence. Over a wide range of offset fields and ramp rates, the measured response is fully consistent with adiabatic behavior. The echo amplitudes exhibit characteristic modulations that are in excellent agreement with theoretical predictions. Non-adiabatic events are observed at distinct offsets.Abruptly after passing through these offsets, the experimental results deviate from the theoretical adiabatic expressions. These non-adiabatic events occur precisely at the field offsets predicted by theory. It is demonstrated that in the adiabatic regime the effects of field fluctuations are fully reversible, while the occurrence of non-adiabatic events leads to hysteresis.The adiabatic range of field offsets can be increased by modifying the refocusing pulses within the CPMG sequence.

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Direct optimization of signal-to-noise ratio of CPMG-like sequences in inhomogeneous fields

Cited by 15 publications

References 36 publications

Training Schrödinger’s cat: quantum optimal control

Training Schrödinger’s cat: quantum optimal control

Adiabatic and nonadiabatic behavior of the Carr-Purcell-Meiboom-Gill sequence in time-dependent magnetic fields

Observation of adiabatic and non-adiabatic behavior for CPMG sequence in time-dependent magnetic fields

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