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Herschel A. Rabitz
Department of Chemistry, Princeton University, Princeton, NJ 08544, USA

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Short Biography

Herschel Rabitz received his Ph.D. in Chemical Physics from Harvard University in 1970. In 1971, Professor Rabitz joined the faculty of the Princeton University Department of Chemistry, and from 1993 to 1996, he was chair of the department. He is also an affiliated member of Princeton University’s Program in Applied and Computational Mathematics. Professor Rabitz’s research interests lie at the interface of chemistry, physics, and engineering, with principal areas of focus including molecular dynamics, biophysical chemistry, chemical kinetics, optical interactions with matter, and molecular scale systems analysis.

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Journal article
Published: 24 August 2021 in COVID
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In recent work, we proposed that effective therapeutic drugs aimed at treating the SARS-CoV-2 infection could be developed based on interdicting in the early steps of the folding pathway of key viral proteins, including the receptor binding domain (RBD) of the spike protein. In order to provide for a drug target on the protein, the earliest contact-formation event along the dominant folding pathway of the RBD spike protein was predicted employing the Sequential Collapse Model (SCM). The segments involved in the predicted earliest contact were suggested to provide optimal folding interdiction target regions (FITRs) for potential therapeutic drugs, with a focus on folding interdicting peptides (FIPs). In this paper, we extend our analysis to include 13 known single mutations of the RBD spike protein as well as the triple mutation B1.351 and the recent double mutation B1.617.2. The results show that the location of the FITR does not change in any of the 15 studied mutations, providing for a mutation-resistant drug design strategy for the RBD-spike protein.

ACS Style

Fernando Bergasa-Caceres; Herschel A. Rabitz. The Promise of Mutation Resistant Drugs for SARS-CoV-2 That Interdict in the Folding of the Spike Protein Receptor Binding Domain. COVID 2021, 1, 288 -302.

AMA Style

Fernando Bergasa-Caceres, Herschel A. Rabitz. The Promise of Mutation Resistant Drugs for SARS-CoV-2 That Interdict in the Folding of the Spike Protein Receptor Binding Domain. COVID. 2021; 1 (1):288-302.

Chicago/Turabian Style

Fernando Bergasa-Caceres; Herschel A. Rabitz. 2021. "The Promise of Mutation Resistant Drugs for SARS-CoV-2 That Interdict in the Folding of the Spike Protein Receptor Binding Domain." COVID 1, no. 1: 288-302.

Journal article
Published: 10 August 2021 in International Journal of Molecular Sciences
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The initial steps of the folding pathway of the C-terminal domain of the murine prion protein mPrP(90–231) are predicted based on the sequential collapse model (SCM). A non-local dominant contact is found to form between the connecting region between helix 1 and β-sheet 1 and the C-terminal region of helix 3. This non-local contact nucleates the most populated molten globule-like intermediate along the folding pathway. A less stable early non-local contact between segments 120–124 and 179–183, located in the middle of helix 2, promotes the formation of a less populated molten globule-like intermediate. The formation of the dominant non-local contact constitutes an example of the postulated Nature’s Shortcut to the prion protein collapse into the native structure. The possible role of the less populated molten globule-like intermediate is explored as the potential initiation point for the folding for three pathogenic mutants (T182A, I214V, and Q211P in mouse prion numbering) of the prion protein.

ACS Style

Fernando Bergasa-Caceres; Herschel Rabitz. Identification of Two Early Folding Stage Prion Non-Local Contacts Suggested to Serve as Key Steps in Directing the Final Fold to Be Either Native or Pathogenic. International Journal of Molecular Sciences 2021, 22, 8619 .

AMA Style

Fernando Bergasa-Caceres, Herschel Rabitz. Identification of Two Early Folding Stage Prion Non-Local Contacts Suggested to Serve as Key Steps in Directing the Final Fold to Be Either Native or Pathogenic. International Journal of Molecular Sciences. 2021; 22 (16):8619.

Chicago/Turabian Style

Fernando Bergasa-Caceres; Herschel Rabitz. 2021. "Identification of Two Early Folding Stage Prion Non-Local Contacts Suggested to Serve as Key Steps in Directing the Final Fold to Be Either Native or Pathogenic." International Journal of Molecular Sciences 22, no. 16: 8619.

Original research article
Published: 19 June 2021 in Risk Analysis
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This work investigates aspects of the global sensitivity analysis of computer codes when alternative plausible distributions for the model inputs are available to the analyst. Analysts may decide to explore results under each distribution or to aggregate the distributions, assigning, for instance, a mixture. In the first case, we lose uniqueness of the sensitivity measures, and in the second case, we lose independence even if the model inputs are independent under each of the assigned distributions. Removing the unique distribution assumption impacts the mathematical properties at the basis of variance-based sensitivity analysis and has consequences on result interpretation as well. We analyze in detail the technical aspects. From this investigation, we derive corresponding recommendations for the risk analyst. We show that an approach based on the generalized functional ANOVA expansion remains theoretically grounded in the presence of a mixture distribution. Numerically, we base the construction of the generalized function ANOVA effects on the diffeomorphic modulation under observable response preserving homotopy regression. Our application addresses the calculation of variance-based sensitivity measures for the well-known Nordhaus' DICE model, when its inputs are assigned a mixture distribution. A discussion of implications for the risk analyst and future research perspectives closes the work.

ACS Style

Emanuele Borgonovo; Genyuan Li; John Barr; Elmar Plischke; Herschel Rabitz. Global Sensitivity Analysis with Mixtures: A Generalized Functional ANOVA Approach. Risk Analysis 2021, 1 .

AMA Style

Emanuele Borgonovo, Genyuan Li, John Barr, Elmar Plischke, Herschel Rabitz. Global Sensitivity Analysis with Mixtures: A Generalized Functional ANOVA Approach. Risk Analysis. 2021; ():1.

Chicago/Turabian Style

Emanuele Borgonovo; Genyuan Li; John Barr; Elmar Plischke; Herschel Rabitz. 2021. "Global Sensitivity Analysis with Mixtures: A Generalized Functional ANOVA Approach." Risk Analysis , no. : 1.

Article
Published: 01 June 2021 in Physical Review Research
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Optimally-shaped electromagnetic fields have the capacity to coherently control the dynamics of quantum systems and thus offer a promising means for controlling molecular transformations relevant to chemical, biological, and materials applications. Currently, advances in this area are hindered by the prohibitive cost of the quantum dynamics simulations needed to explore the principles and possibilities of molecular control. However, the emergence of nascent quantum-computing devices suggests that efficient simulations of quantum dynamics may be on the horizon. In this article, we study how quantum computers could be employed to design optimally-shaped fields to control molecular systems. We introduce a hybrid algorithm that utilizes a quantum computer for simulating the field-induced quantum dynamics of a molecular system in polynomial time, in combination with a classical optimization approach for updating the field. Qubit encoding methods relevant for molecular control problems are described, and procedures for simulating the quantum dynamics and obtaining the simulation results are discussed. Numerical illustrations are then presented that explicitly treat paradigmatic vibrational and rotational control problems, and also consider how optimally-shaped fields could be used to elucidate the mechanisms of energy transfer in light-harvesting complexes. Resource estimates, as well as a numerical assessment of the impact of hardware noise and the prospects of near-term hardware implementations, are provided for the latter task.

ACS Style

Alicia B. Magann; Matthew D. Grace; Herschel A. Rabitz; Mohan Sarovar. Digital quantum simulation of molecular dynamics and control. Physical Review Research 2021, 3, 023165 .

AMA Style

Alicia B. Magann, Matthew D. Grace, Herschel A. Rabitz, Mohan Sarovar. Digital quantum simulation of molecular dynamics and control. Physical Review Research. 2021; 3 (2):023165.

Chicago/Turabian Style

Alicia B. Magann; Matthew D. Grace; Herschel A. Rabitz; Mohan Sarovar. 2021. "Digital quantum simulation of molecular dynamics and control." Physical Review Research 3, no. 2: 023165.

Original research article
Published: 11 May 2021 in Frontiers in Physics
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We investigate the control landscapes of closed n-level quantum systems beyond the dipole approximation by including a polarizability term in the Hamiltonian. The latter term is quadratic in the control field. Theoretical analysis of singular controls is presented, which are candidates for producing landscape traps. The results for considering the presence of singular controls are compared to their counterparts in the dipole approximation (i.e., without polarizability). A numerical analysis of the existence of traps in control landscapes for generating unitary transformations beyond the dipole approximation is made upon including the polarizability term. An extensive exploration of these control landscapes is achieved by creating many random Hamiltonians which include terms linear and quadratic in a single control field. The discovered singular controls are all found not to be local optima. This result extends a great body of recent work on typical landscapes of quantum systems where the dipole approximation is made. We further investigate the relationship between the magnitude of the polarizability and the fluence of the control resulting from optimization. It is also shown that including a polarizability term in an otherwise uncontrollable dipole coupled system removes traps from the corresponding control landscape by restoring controllability. We numerically assess the effect of a polarizability term on a known example of a particular three-level Λ-system with a second order trap in its control landscape. It is found that the addition of the polarizability removes the trap from the landscape. The general practical control implications of these simulations are discussed.

ACS Style

Benjamin Russell; Re-Bing Wu; Herschel Rabitz. Quantum Control Landscapes Beyond the Dipole Approximation: Controllability, Singular Controls, and Resources. Frontiers in Physics 2021, 9, 1 .

AMA Style

Benjamin Russell, Re-Bing Wu, Herschel Rabitz. Quantum Control Landscapes Beyond the Dipole Approximation: Controllability, Singular Controls, and Resources. Frontiers in Physics. 2021; 9 ():1.

Chicago/Turabian Style

Benjamin Russell; Re-Bing Wu; Herschel Rabitz. 2021. "Quantum Control Landscapes Beyond the Dipole Approximation: Controllability, Singular Controls, and Resources." Frontiers in Physics 9, no. : 1.

Article
Published: 12 January 2021 in Physical Review A
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We present a systematic study of quantum system compression for the evolution of generic many-body problems. The necessary numerical simulations of such systems are seriously hindered by the exponential growth of the Hilbert-space dimension with the number of particles. For a constant Hamiltonian system of Hilbert-space dimension n with frequencies ranging from fmin to fmax, we show via a proper orthogonal decomposition that for a run time T the dominant dynamics are compressed in the neighborhood of a subspace whose dimension is the smallest integer larger than the time-bandwidth product Δ=(fmax−fmin)T. We also show how the distribution of initial states can further compress the system dimension. Under the stated conditions, the time-bandwidth estimate reveals the existence of an effective compressed model whose dimension is derived solely from system properties and not dependent on the particular implementation of a variational simulator, such as a machine learning system, or quantum device, or possibly even specially adapting traditional methods of solving the time-dependent Schrödinger equation. However, finding an efficient solution procedure is dependent on the simulator implementation, which is not discussed in this paper. In addition, we show that the compression rendered by the proper orthogonal decomposition encoding method can be further strengthened via a multilayer autoencoder. Finally, we present numerical illustrations to affirm the compression behavior in time-varying Hamiltonian dynamics in the presence of external fields. The essential time-bandwidth product is also simply estimated for a wide class of physical systems, where typically localized high-frequency motion occurs at or around each of the many particles, and with low-frequency dynamics associated with globally distributed characteristic degrees of freedom. This estimate for the bandwidth has a generic character indicating the wide significance of expected quantum system dynamics compression. We also discuss the potential implications of the findings for machine learning tools to efficiently solve the many-body or other high-dimensional Schrödinger equations.

ACS Style

Robert L. Kosut; Tak-San Ho; Herschel Rabitz. Quantum system compression: A Hamiltonian guided walk through Hilbert space. Physical Review A 2021, 103, 012406 .

AMA Style

Robert L. Kosut, Tak-San Ho, Herschel Rabitz. Quantum system compression: A Hamiltonian guided walk through Hilbert space. Physical Review A. 2021; 103 (1):012406.

Chicago/Turabian Style

Robert L. Kosut; Tak-San Ho; Herschel Rabitz. 2021. "Quantum system compression: A Hamiltonian guided walk through Hilbert space." Physical Review A 103, no. 1: 012406.

Article
Published: 12 January 2021 in PRX Quantum
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The last decade has witnessed remarkable progress in the development of quantum technologies. Although fault-tolerant devices likely remain years away, the noisy intermediate-scale quantum devices of today may be leveraged for other purposes. Leading candidates are variational quantum algorithms (VQAs), which have been developed for applications including chemistry, optimization, and machine learning, but whose implementations on quantum devices have yet to demonstrate improvements over classical capabilities. In this Perspective, we propose a variety of ways that the performance of VQAs could be informed by quantum optimal control theory. A major theme throughout is the need for sufficient control resources in VQA implementations; we discuss different ways this need can manifest, outline a variety of open questions, and look to the future.

ACS Style

Alicia B. Magann; Christian Arenz; Matthew D. Grace; Tak-San Ho; Robert L. Kosut; Jarrod R. McClean; Herschel A. Rabitz; Mohan Sarovar. From Pulses to Circuits and Back Again: A Quantum Optimal Control Perspective on Variational Quantum Algorithms. PRX Quantum 2021, 2, 010101 .

AMA Style

Alicia B. Magann, Christian Arenz, Matthew D. Grace, Tak-San Ho, Robert L. Kosut, Jarrod R. McClean, Herschel A. Rabitz, Mohan Sarovar. From Pulses to Circuits and Back Again: A Quantum Optimal Control Perspective on Variational Quantum Algorithms. PRX Quantum. 2021; 2 (1):010101.

Chicago/Turabian Style

Alicia B. Magann; Christian Arenz; Matthew D. Grace; Tak-San Ho; Robert L. Kosut; Jarrod R. McClean; Herschel A. Rabitz; Mohan Sarovar. 2021. "From Pulses to Circuits and Back Again: A Quantum Optimal Control Perspective on Variational Quantum Algorithms." PRX Quantum 2, no. 1: 010101.

Journal article
Published: 11 January 2021 in Applied Physics Letters
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Conventionally, bidirectional optogenetic switches are controlled with linear excitation (e.g., monochromatic CW light), which has serious limitations when there is a spectral overlap between the “on” and “off” states of the switch. The spectral crosstalk lowers the selectivity of the photoactivation step, resulting in a moderate photoequilibrium value and a poor dynamic range for the switch. Using stimulated depletion quenching (SDQ), which is a nonlinear optical strategy similar to STED, we demonstrate enhanced photoactivation selectivity on one side of the switch, thus shifting the photoequilibrium beyond what is achievable with CW light. The discussion is built around Cph8 as a prototypical bidirectional optogenetic switch lacking complete photoreversibility upon CW excitation because of the spectral crosstalk. We use two fluorescent dyes as analogues to emulate the key spectral feature of the on and off states of Cph8; in this way, we focus on the initial photoactivation step and abstract from the complicated subsequent dynamics. By applying SDQ to a mixture of the dyes, we enhance the selectivity of the photoactivation beyond the linear regime. Increased selectivity of the photoactivation step via nonlinear optical techniques should translate into an improved dynamic range for a broad variety of bidirectional switches. These experiments provide a basis to further expand the foundations for non-conventional optical control methods of biological switching.

ACS Style

Yisen Wang; Alexei Goun; Francois LaForge; Zachary Quine; Herschel Rabitz. A key bidirectional switching issue in optogenetics emulated with laser dyes to illustrate its mitigation using nonlinear optical tools. Applied Physics Letters 2021, 118, 024101 .

AMA Style

Yisen Wang, Alexei Goun, Francois LaForge, Zachary Quine, Herschel Rabitz. A key bidirectional switching issue in optogenetics emulated with laser dyes to illustrate its mitigation using nonlinear optical tools. Applied Physics Letters. 2021; 118 (2):024101.

Chicago/Turabian Style

Yisen Wang; Alexei Goun; Francois LaForge; Zachary Quine; Herschel Rabitz. 2021. "A key bidirectional switching issue in optogenetics emulated with laser dyes to illustrate its mitigation using nonlinear optical tools." Applied Physics Letters 118, no. 2: 024101.

Article
Published: 07 December 2020 in Physical Review A
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Designing a high-quality control is crucial for reliable quantum computation. Among the existing approaches, closed-loop leaning control is an effective choice. Its efficiency depends on the learning algorithm employed, thus deserving algorithmic comparisons for its practical applications. Here we assess three representative learning algorithms, including GRadient Ascent Pulse Engineering (GRAPE), improved Nelder-Mead (NMplus), and Differential Evolution (DE), by searching for high-quality control pulses to prepare the Bell state. We first implement each algorithm experimentally in a nuclear magnetic resonance system and then conduct a numerical study considering the impact of some possible significant experimental uncertainties. The experiments report the successful preparation of the high-fidelity target state by the three algorithms, while NMplus converges fastest, and these results coincide with the numerical simulations when potential uncertainties are negligible. However, under certain significant uncertainties, these algorithms possess distinct performance with respect to their resulting precision and efficiency, and DE shows the best robustness. This study provides insight to aid in the practical application of different closed-loop learning algorithms in realistic physical scenarios.

ACS Style

Xiao-Dong Yang; Christian Arenz; Istvan Pelczer; Qi-Ming Chen; Re-Bing Wu; Xinhua Peng; Herschel Rabitz. Assessing three closed-loop learning algorithms by searching for high-quality quantum control pulses. Physical Review A 2020, 102, 062605 .

AMA Style

Xiao-Dong Yang, Christian Arenz, Istvan Pelczer, Qi-Ming Chen, Re-Bing Wu, Xinhua Peng, Herschel Rabitz. Assessing three closed-loop learning algorithms by searching for high-quality quantum control pulses. Physical Review A. 2020; 102 (6):062605.

Chicago/Turabian Style

Xiao-Dong Yang; Christian Arenz; Istvan Pelczer; Qi-Ming Chen; Re-Bing Wu; Xinhua Peng; Herschel Rabitz. 2020. "Assessing three closed-loop learning algorithms by searching for high-quality quantum control pulses." Physical Review A 102, no. 6: 062605.

Preprint content
Published: 10 September 2020
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We discuss some critical events of the origins of life using a mathematical model and simulation studies. We find that for a replicating population of RNA molecules participating in template-directed polymerization, the hitting and establishment of a high-fidelity replicator depends critically on the polymerase fitness and sequence specificity landscapes and on genome dimension. Probability of hitting is dominated by polymerase landscape curvature, whereas hitting time is dominated by genome dimension. Surface chemistries, compartmentalization, and decay increase hitting times. These results suggest replication to be the first privileged function marking the start of Darwinian evolution, possibly in conjunction with clay minerals or preceded by metabolism, whose dynamics evolved mostly during the final period of the search.

ACS Style

Caleb Deen Bastian; Herschel Rabitz. Critical events of the origins of life. 2020, 1 .

AMA Style

Caleb Deen Bastian, Herschel Rabitz. Critical events of the origins of life. . 2020; ():1.

Chicago/Turabian Style

Caleb Deen Bastian; Herschel Rabitz. 2020. "Critical events of the origins of life." , no. : 1.

Journal article
Published: 02 September 2020 in IEEE Transactions on Control Systems Technology
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We investigate two classes of quantum control problems by using frequency-domain optimization algorithms in the context of ultrafast laser control of quantum systems. In the first class of problems, the system model is known and a frequency-domain gradient-based optimization algorithm is applied for searching an optimal control field to selectively and robustly manipulate the population transfer in atomic rubidium. The other class of quantum control problems involves an experimental system with an unknown model. In this case, we introduce a differential evolution algorithm with a mixed strategy to search for optimal control fields and demonstrate the capability in an ultrafast laser control experiment for the fragmentation of Pr(hfac)₃ molecules.

ACS Style

Daoyi Dong; Chuan-Cun Shu; Jiangchao Chen; Xi Xing; Hailan Ma; Yu Guo; Herschel Rabitz. Learning Control of Quantum Systems Using Frequency-Domain Optimization Algorithms. IEEE Transactions on Control Systems Technology 2020, 29, 1791 -1798.

AMA Style

Daoyi Dong, Chuan-Cun Shu, Jiangchao Chen, Xi Xing, Hailan Ma, Yu Guo, Herschel Rabitz. Learning Control of Quantum Systems Using Frequency-Domain Optimization Algorithms. IEEE Transactions on Control Systems Technology. 2020; 29 (4):1791-1798.

Chicago/Turabian Style

Daoyi Dong; Chuan-Cun Shu; Jiangchao Chen; Xi Xing; Hailan Ma; Yu Guo; Herschel Rabitz. 2020. "Learning Control of Quantum Systems Using Frequency-Domain Optimization Algorithms." IEEE Transactions on Control Systems Technology 29, no. 4: 1791-1798.

Research article
Published: 10 August 2020 in The Journal of Physical Chemistry B
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In this article we predict the folding initiation events of the ribose phosphatase domain of protein Nsp3 and the receptor binding domain of the spike protein from the SARS Coronavirus-2. The calculations employ the Sequential Collapse Model (SCM), and the crystal structures to identify the segments involved in the initial contact formation events of both viral proteins. The initial contact locations may provide good targets for therapeutic drug development. The proposed strategy is based on a drug binding to the contact location thereby aiming to prevent protein folding. Peptides are suggested as a natural choice for such protein folding interdiction drugs.

ACS Style

Fernando Bergasa-Caceres; Herschel A. Rabitz. Interdiction of Protein Folding for Therapeutic Drug Development in SARS CoV-2. The Journal of Physical Chemistry B 2020, 124, 8201 -8208.

AMA Style

Fernando Bergasa-Caceres, Herschel A. Rabitz. Interdiction of Protein Folding for Therapeutic Drug Development in SARS CoV-2. The Journal of Physical Chemistry B. 2020; 124 (38):8201-8208.

Chicago/Turabian Style

Fernando Bergasa-Caceres; Herschel A. Rabitz. 2020. "Interdiction of Protein Folding for Therapeutic Drug Development in SARS CoV-2." The Journal of Physical Chemistry B 124, no. 38: 8201-8208.

Article
Published: 30 July 2020 in Physical Review A
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This paper presents a method for performing approximate optimal control simulations for quantum systems with multiple coupled degrees of freedom. The time evolution is simulated using the first-order Magnus expansion in the interaction picture, where the couplings between different degrees of freedom are treated as the perturbation. A numerical implementation procedure is presented that leverages upon pairwise couplings and the separability of the zeroth-order time evolution operator to achieve a reduced computational cost, which is analyzed with respect to the number of degrees of freedom. The formulation is compatible with gradient-free methods to optimize the control field, and a stochastic hill climbing algorithm is adopted for this purpose. As illustrations, optimal control simulations are performed for systems of two and three dipole-dipole-coupled molecular rotors under the influence of a control field. For the two-rotor system, the field is optimized to achieve either orientation or entanglement objectives. For the three-rotor system, the field is optimized either to orient all three rotors in the same direction or to orient one rotor in a particular direction while the other two rotors point in the opposite direction.

ACS Style

Andrew Ma; Alicia B. Magann; Tak-San Ho; Herschel Rabitz. Optimal control of coupled quantum systems based on the first-order Magnus expansion: Application to multiple dipole-dipole-coupled molecular rotors. Physical Review A 2020, 102, 013115 .

AMA Style

Andrew Ma, Alicia B. Magann, Tak-San Ho, Herschel Rabitz. Optimal control of coupled quantum systems based on the first-order Magnus expansion: Application to multiple dipole-dipole-coupled molecular rotors. Physical Review A. 2020; 102 (1):013115.

Chicago/Turabian Style

Andrew Ma; Alicia B. Magann; Tak-San Ho; Herschel Rabitz. 2020. "Optimal control of coupled quantum systems based on the first-order Magnus expansion: Application to multiple dipole-dipole-coupled molecular rotors." Physical Review A 102, no. 1: 013115.

Article
Published: 11 May 2020 in Physical Review A
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High-precision operation of quantum computing systems must be robust to uncertainties and noises in the quantum hardware. We show that through a game played between the uncertainties (or noises) and the controls, adversarial uncertainty samples can be generated to find highly robust controls through the search for Nash equilibria. We propose a broad family of adversarial learning algorithms, namely a-GRAPE algorithms, which includes two effective learning schemes referred to as the best-response approach and the better-response approach within game-theoretic terminology, providing options for learning highly robust controls. Numerical experiments demonstrate that the balance between fidelity and robustness depends on the details of the chosen adversarial learning algorithm, which can effectively lead to a significant enhancement of control robustness while attaining high fidelity.

ACS Style

Xiaozhen Ge; Haijin Ding; Herschel Rabitz; Re-Bing Wu. Robust quantum control in games: An adversarial learning approach. Physical Review A 2020, 101, 052317 .

AMA Style

Xiaozhen Ge, Haijin Ding, Herschel Rabitz, Re-Bing Wu. Robust quantum control in games: An adversarial learning approach. Physical Review A. 2020; 101 (5):052317.

Chicago/Turabian Style

Xiaozhen Ge; Haijin Ding; Herschel Rabitz; Re-Bing Wu. 2020. "Robust quantum control in games: An adversarial learning approach." Physical Review A 101, no. 5: 052317.

Journal article
Published: 27 April 2020 in Scientific Reports
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The photo-induced dissociative-ionization of lanthanide complexes Ln(hfac)3 (Ln = Pr, Er, Yb) is studied using intense ultrafast transform limited (TL) and linearly chirped laser pulses in a time-of-flight (TOF) mass spectrometry setup. Various fluorine and Ln-containing high-mass fragments were observed in this experiment, including the molecular parent ion, which have not been seen with previous studies relying on relatively long-duration laser pulses (i.e., ns or longer). These new high-mass observations provide important formerly missing information for deducing a set of photo-fragmentation mechanistic pathways for Ln(hfac)3. An overall ultrafast control mechanism is proposed by combining insights from earlier studies and the fragments observed in this research to result in three main distinct photo-fragmentation processes: (a) ligand-metal charge transfer, (b) CF3 elimination, and (c) C-C bond rotation processes. We conclude that ultrafast dissociative-ionization could be a promising technique for generating high-mass fragments for potential use in material science applications.

ACS Style

Jiangchao Chen; Xi Xing; Roberto Rey-De-Castro; Herschel Rabitz. Ultrafast Photofragmentation of Ln(hfac)3 with a Proposed Mechanism for forming High Mass Fluorinated Products. Scientific Reports 2020, 10, 1 -8.

AMA Style

Jiangchao Chen, Xi Xing, Roberto Rey-De-Castro, Herschel Rabitz. Ultrafast Photofragmentation of Ln(hfac)3 with a Proposed Mechanism for forming High Mass Fluorinated Products. Scientific Reports. 2020; 10 (1):1-8.

Chicago/Turabian Style

Jiangchao Chen; Xi Xing; Roberto Rey-De-Castro; Herschel Rabitz. 2020. "Ultrafast Photofragmentation of Ln(hfac)3 with a Proposed Mechanism for forming High Mass Fluorinated Products." Scientific Reports 10, no. 1: 1-8.

Accepted manuscript
Published: 10 February 2020 in Journal of Physics A: Mathematical and Theoretical
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We derive an upper bound for the time needed to implement a generic unitary transformation in a $d$ dimensional quantum system using $d$ control fields. We show that given the ability to control the diagonal elements of the Hamiltonian, which allows for implementing any unitary transformation under the premise of controllability, the time $T$ needed is upper bounded by $T\leq \frac{\pi d^{2}(d-1)}{2g_{\text{min}}}$ where $g_{\text{min}}$ is the smallest coupling constant present in the system. We study the tightness of the bound by numerically investigating randomly generated systems, with specific focus on a system consisting of $d$ energy levels that interact in a tight-binding like manner.

ACS Style

Juneseo Lee; Christian Arenz; Daniel K Burgarth; Herschel Rabitz. An upper bound on the time required to implement unitary operations. Journal of Physics A: Mathematical and Theoretical 2020, 53, 125304 .

AMA Style

Juneseo Lee, Christian Arenz, Daniel K Burgarth, Herschel Rabitz. An upper bound on the time required to implement unitary operations. Journal of Physics A: Mathematical and Theoretical. 2020; 53 (12):125304.

Chicago/Turabian Style

Juneseo Lee; Christian Arenz; Daniel K Burgarth; Herschel Rabitz. 2020. "An upper bound on the time required to implement unitary operations." Journal of Physics A: Mathematical and Theoretical 53, no. 12: 125304.

Journal article
Published: 20 August 2019 in Chemical Physics
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We consider laser-driven optimal control landscape of a molecule from a classical mechanical perspective. The goal of optimal control in the present work is to steer the molecule from an initial state to a target state, denoted by two distinct points in phase space. Thus, a particular control objective is given as the difference between the final achieved phase space point and the target. The corresponding control landscape is defined as the latter control objective as a functional of the control field. While previous examination of the landscape critical points (i.e., a suboptimal point on the landscape where there is a zero gradient) has shown that the landscape topology is generally trap-free, the structure of the landscape away from these critical points is not well understood. We explore the landscape structure by examining an underlying metric defined as the ratio R of the gradient-based optimization path length of the control field evolution to the Euclidean distance between a given initial control field and the resultant optimal control field, where the latter field corresponds to a point at the top of the landscape. We analyze the path length-to-distance ratio R analytically for a linear forced harmonic oscillator and numerically for a nonlinear forced Morse oscillator. For the linear forced harmonic oscillator, we find that R⩽2 and reaches its minimum value of 1 (i.e., corresponding to “a straight shot” through control space) in the large target time limit, as well as at special finite target times. The ratio R is similarly small for Morse oscillator simulations when following a steepest-ascent path to the top of the landscape, implying that the landscape is quite smooth and devoid of gnarled features. This conclusion is exemplified for a path discovered with R≃1.0 where simply following the initial gradient direction takes the climb very close to the top of the landscape. These findings are consistent with a variety of previous like simulations examining R in quantum control scenarios.

ACS Style

Carlee Joe-Wong; Tak-San Ho; Herschel Rabitz. Assessing the structure of classical molecular optimal control landscapes. Chemical Physics 2019, 527, 110504 .

AMA Style

Carlee Joe-Wong, Tak-San Ho, Herschel Rabitz. Assessing the structure of classical molecular optimal control landscapes. Chemical Physics. 2019; 527 ():110504.

Chicago/Turabian Style

Carlee Joe-Wong; Tak-San Ho; Herschel Rabitz. 2019. "Assessing the structure of classical molecular optimal control landscapes." Chemical Physics 527, no. : 110504.

Journal article
Published: 12 August 2019 in IEEE Transactions on Automatic Control
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A quantum state filter (QSF) is proposed in this paper to estimate a low-rank quantum density matrix from informationally incomplete and contaminated measurements. There exist sparse disturbances on the quantum density matrix and Gaussian noise in the measurements. A proximal Jacobian variant of the alternating direction method of multipliers (PJADMM) is proposed to design the QSF. The closed-form solutions to three resulting subproblems are given and the iterative QSF is developed. The proposed QSF is proved to be convergent and its superiority is demonstrated in the numerical illustrations compared with different state-of-the-art methods.

ACS Style

Jiaojiao Zhang; Shuang Cong; Qing Ling; Kezhi Li; Herschel Rabitz. Quantum State Filter With Disturbance and Noise. IEEE Transactions on Automatic Control 2019, 65, 2856 -2866.

AMA Style

Jiaojiao Zhang, Shuang Cong, Qing Ling, Kezhi Li, Herschel Rabitz. Quantum State Filter With Disturbance and Noise. IEEE Transactions on Automatic Control. 2019; 65 (7):2856-2866.

Chicago/Turabian Style

Jiaojiao Zhang; Shuang Cong; Qing Ling; Kezhi Li; Herschel Rabitz. 2019. "Quantum State Filter With Disturbance and Noise." IEEE Transactions on Automatic Control 65, no. 7: 2856-2866.

Journal article
Published: 10 July 2019 in IEEE Transactions on Cybernetics
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Robust control design for quantum systems has been recognized as a key task in quantum information technology, molecular chemistry, and atomic physics. In this paper, an improved differential evolution algorithm, referred to as multiple-samples and mixed-strategy DE (msMS_DE), is proposed to search robust fields for various quantum control problems. In msMS_DE, multiple samples are used for fitness evaluation and a mixed strategy is employed for the mutation operation. In particular, the msMS_DE algorithm is applied to the control problems of: 1) open inhomogeneous quantum ensembles and 2) the consensus goal of a quantum network with uncertainties. Numerical results are presented to demonstrate the excellent performance of the improved machine learning algorithm for these two classes of quantum robust control problems. Furthermore, msMS_DE is experimentally implemented on femtosecond (fs) laser control applications to optimize two-photon absorption and control fragmentation of the molecule CH₂BrI. The experimental results demonstrate the excellent performance of msMS_DE in searching for effective fs laser pulses for various tasks.

ACS Style

Daoyi Dong; Xi Xing; Hailan Ma; Chunlin Chen; Zhixin Liu; Herschel Rabitz. Learning-Based Quantum Robust Control: Algorithm, Applications, and Experiments. IEEE Transactions on Cybernetics 2019, 50, 3581 -3593.

AMA Style

Daoyi Dong, Xi Xing, Hailan Ma, Chunlin Chen, Zhixin Liu, Herschel Rabitz. Learning-Based Quantum Robust Control: Algorithm, Applications, and Experiments. IEEE Transactions on Cybernetics. 2019; 50 (8):3581-3593.

Chicago/Turabian Style

Daoyi Dong; Xi Xing; Hailan Ma; Chunlin Chen; Zhixin Liu; Herschel Rabitz. 2019. "Learning-Based Quantum Robust Control: Algorithm, Applications, and Experiments." IEEE Transactions on Cybernetics 50, no. 8: 3581-3593.

Journal article
Published: 21 June 2019 in Journal of the Optical Society of America B
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It is well known that gold nanorods (AuNRs) readily emit two-photon luminescence (TPL) when excited by a broad bandwidth laser pulse that is tuned to the AuNRs’ localized surface plasmon resonance. The nature of the mechanism (i.e., especially its degree of coherence) is under active debate. In this work, we measured the TPL emission from single nanorods while varying the angle θ between the linearly polarized laser electric field and the nanorod’s orientation. Data were best fit with a linear combination of cos4 θ and cos2 θ functions. While the former function may represent TPL signals arising from both coherent and incoherent processes, the later function is indicative of a purely incoherent process. To further validate this assessment, we measured TPL emission from single nanorods in a time-resolved collinear autocorrelation setup. The autocorrelation signal exhibited a large peak at zero delay, which is characteristic of coherent two-photon absorption and two lower intensity wings extending to a few picoseconds, which demonstrates the existence of a long-lived intermediate state that contributes to a two-step incoherent absorption process. We conclude that TPL in AuNRs can result from a combination of coherent and incoherent absorption processes.

ACS Style

Dan Xie; François O. LaForge; Ilya Grigorenko; Herschel A. Rabitz. Dual coherent and incoherent two-photon luminescence in single gold nanorods revealed by polarization and time-resolved nonlinear autocorrelation. Journal of the Optical Society of America B 2019, 36, 1931 -1936.

AMA Style

Dan Xie, François O. LaForge, Ilya Grigorenko, Herschel A. Rabitz. Dual coherent and incoherent two-photon luminescence in single gold nanorods revealed by polarization and time-resolved nonlinear autocorrelation. Journal of the Optical Society of America B. 2019; 36 (7):1931-1936.

Chicago/Turabian Style

Dan Xie; François O. LaForge; Ilya Grigorenko; Herschel A. Rabitz. 2019. "Dual coherent and incoherent two-photon luminescence in single gold nanorods revealed by polarization and time-resolved nonlinear autocorrelation." Journal of the Optical Society of America B 36, no. 7: 1931-1936.