Optimal Control of Spin Qudits Subject to Decoherence Using Amplitude-and-Frequency-Constrained Pulses (2403.15785v2)
Abstract: Quantum optimal control theory (QOCT) can be used to design the shape of electromagnetic pulses that implement operations on quantum devices. By using non-trivially shaped waveforms, gates can be made significantly faster than those built by concatenating monochromatic pulses. Recently, we applied this technique to the control of molecular spin qudits modelled with Schr\"odinger's equation and showed it can speed up operations, helping mitigate the effects of decoherence [Phys. Rev. Appl. 17, 064028 (2022)]. However, short gate times result in large optimal pulse amplitudes, which may not be experimentally accessible. Introducing bounds to the amplitudes then unavoidably leads to longer operation times, for which decoherence can no longer be neglected. Here, we study how to improve this procedure by applying QOCT on top of Lindblad's equation, to design control pulses accounting for decoherence already in the optimization process. In addition, we introduce a formulation that allows us to bound the maximum amplitude and frequency of the signals, which are the typical limitations of waveform generators. The pulses we obtain consistently enhance operation fidelities compared to those achieved with Schr\"odinger's equation across various target gates and durations, demonstrating the flexibility and robustness of our method. The improvement is larger the shorter the spin coherence time $T_{2}$.
- E. Knill and R. Laflamme, Theory of quantum error-correcting codes, Phys. Rev. A 55, 900 (1997).
- Google Quantum AI, Suppressing quantum errors by scaling a surface code logical qubit, Nature 614, 676 (2023).
- D. Gottesman, A. Kitaev, and J. Preskill, Encoding a qubit in an oscillator, Phys. Rev. A 64, 012310 (2001).
- M. N. Leuenberger and D. Loss, Quantum computing in molecular magnets, Nature 410, 789 (2001).
- G. K. Brennen, D. P. O’Leary, and S. S. Bullock, Criteria for exact qudit universality, Phys. Rev. A 71, 052318 (2005).
- D. Gatteschi and R. Sessoli, Quantum tunneling of magnetization and related phenomena in molecular materials, Angew. Chem., Int. Ed. 42, 268 (2003).
- M. Atzori and R. Sessoli, The second quantum revolution: Role and challenges of molecular chemistry, J. Am. Chem. Soc. 141, 11339 (2019).
- C. Brif, R. Chakrabarti, and H. Rabitz, Control of quantum phenomena: past present and future, New J. Phys. 12, 075008 (2010).
- R. M. White, Quantum Theory of Magnetism : Magnetic Properties of Materials (Springer Berlin Heidelberg, 2007).
- G. Lindblad, On the generators of quantum dynamical semigroups, Commun. Math. Phys. 48, 119 (1976).
- V. Gorini, A. Kossakowski, and E. C. G. Sudarshan, Completely positive dynamical semigroups of n‐level systems, J. Math. Phys. 17, 821 (1976).
- In this work, we will assume that the purpose is to realize a given gate in the interaction representation.
- M. H. Goerz, D. M. Reich, and C. P. Koch, Optimal control theory for a unitary operation under dissipative evolution, New J. Phys. 16, 055012 (2014).
- A. Castro, qocttools: A program for quantum optimal control calculations, Comput. Phys. Commun. 295, 108983 (2024).
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