Prethermal quasiconserved observables in Floquet quantum systems

Yin, Chao; Peng, Pai; Huang, Xiaoyang; Ramanathan, Chandrasekhar; Cappellaro, Paola

doi:10.1103/physrevb.103.054305

Cited by 18 publications

(7 citation statements)

References 85 publications

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“…A flurry of theoretical work has recognized Floquet prethermalization under random driving [13], in driven linear chains [9], and even in the classical limit [14]. Experimentally, Floquet prethermalization has been observed in cold-atom [15][16][17] and NMR systems [18][19][20]. They demonstrated a characteristic exponential suppression of heating rates with Floquet driving.…”

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confidence: 99%

“…Even before the current resurgence of interest, decadesold NMR experiments had probed thermalization dynamics in driven nuclear systems [25,26]. The vast preponderance of NMR experiments have, however, been limited to high-𝛾 𝑛 and dense (100% abundant) nuclei such as 19 F, 31 P, and 1 H [18,20]. Instead, we focus attention to dilute networks of insensitive nuclei ( 13 C).…”

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confidence: 99%

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Floquet prethermalization with lifetime exceeding 90s in a bulk hyperpolarized solid

Beatrez,

Janes,

Akkiraju

et al. 2021

Preprint

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We report the observation of long-lived Floquet prethermal states in a bulk solid composed of dipolar-coupled 13 C nuclei in diamond at room temperature. For precessing nuclear spins prepared in an initial transverse state, we demonstrate Floquet control that prevents their decay over multiple-minute long periods. We observe Floquet prethermal lifetimes 𝑇 2 ≈90.9s, extended >60,000-fold over the nuclear free induction decay times. The spins themselves are continuously interrogated for ∼10min, corresponding to the application of ≈5.8M control pulses. The 13 C nuclei are optically hyperpolarized by lattice Nitrogen Vacancy (NV) centers; the combination of hyperpolarization and continuous spin readout yields significant signal-to-noise in the measurements. This allows probing the Floquet thermalization dynamics with unprecedented clarity. We identify four characteristic regimes of the thermalization process, discerning short-time transient processes leading to the prethermal plateau, and long-time system heating towards infinite temperature. This work points to new opportunities possible via Floquet control in networks of dilute, randomly distributed, low-sensitivity nuclei. In particular, the combination of minutes-long prethermal lifetimes and continuous spin interrogation opens avenues for quantum sensors constructed from hyperpolarized Floquet prethermal nuclei.

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confidence: 99%

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confidence: 99%

Floquet prethermalization with lifetime exceeding 90s in a bulk hyperpolarized solid

Beatrez,

Janes,

Akkiraju

et al. 2021

Preprint

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“…to emphasize the small infidelity. The fidelity also provides a lower bound for observable correlations [38,43,44], which can be directly measured in experiments [37], and it is thus a good metric to assess the sequence [20].…”

Section: A Modelingmentioning

confidence: 99%

Deep reinforcement learning for quantum Hamiltonian engineering

Peng¹,

Huang²,

Yin³

et al. 2021

Preprint

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Engineering desired Hamiltonian in quantum many-body systems is essential for applications such as quantum simulation, computation and sensing. Conventional quantum Hamiltonian engineering sequences are designed using human intuition based on perturbation theory, which may not describe the optimal solution and is unable to accommodate complex experimental imperfections. Here we numerically search for Hamiltonian engineering sequences using deep reinforcement learning (DRL) techniques and experimentally demonstrate that they outperform celebrated sequences on a solid-state nuclear magnetic resonance quantum simulator. As an example, we aim at decoupling strongly-interacting spin-1/2 systems. We train DRL agents in the presence of different experimental imperfections and verify robustness of the output sequences both in simulations and experiments. Surprisingly, many of the learned sequences exhibit a common pattern that had not been discovered before, to our knowledge, but has an meaningful analytical description. We can thus restrict the searching space based on this control pattern, allowing to search for longer sequences, ultimately leading to sequences that are robust against dominant imperfections in our experiments. Our results not only demonstrate a general method for quantum Hamiltonian engineering, but also highlight the importance of combining black-box artificial intelligence with understanding of physical system in order to realize experimentally feasible applications.

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“…These phases may even exhibit extraordinary robustness against the transverse perturbations for a relatively long term. Experimental works show the existence of a quasi-conserved observable [10,32], corresponding to the emergent symmetry [33][34][35]. Intuitively, the quasi-conserved observable can be observed in a more sophisticated Floquet system whose symmetry is weakly broken.…”

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confidence: 98%

Floquet Prethermal Phase Protected by U(1) Symmetry on a Superconducting Quantum Processor

Ying,

Guo,

et al. 2021

Preprint

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Periodically driven systems, or Floquet systems, exhibit many novel dynamics and interesting outof-equilibrium phases of matter. Those phases arising with the quantum systems' symmetries, such as global U (1) symmetry, can even show dynamical stability with symmetry-protection. Here we experimentally demonstrate a U (1) symmetry-protected prethermal phase, via performing a digitalanalog quantum simulation on a superconducting quantum processor. The dynamical stability of this phase is revealed by its robustness against external perturbations. We also find that the spin glass order parameter in this phase is stabilized by the interaction between the spins. Our work reveals a promising prospect in discovering emergent quantum dynamical phases with digital-analog quantum simulators.Introduction: Searching for novel phases of matter is an eternal task in the field of condensed matter. In traditional condensed matter theory, all the phases of equilibrium matter were described by Landau's symmetry-breaking theory [1] for a long time until the discovery of topological order [2, 3] broadened the range of states of matter. Recently, an evolution has happened in the field of far-from-equilibrium condensed matter [4][5][6]. The progress of driven quantum time-periodic systems, namely Floquet systems, has stimulated further interest in the search for far-from-equilibrium phases. A conventional view is that, in such a system, the information encoded on the initial state will be rapidly erased due to the inevitable thermalization induced by the continuous driving [7][8][9]. Two important mechanisms have been considered to prevent the information loss and lead to long-lived phases under the Floquet drive: The first is many-body localization (MBL), in which the eigenstate thermalization hypothesis (ETH) falis [9]; The other one is prethermalization, where the thermalization rate is exponentially small [9][10][11]. Phenomena of prethermalization have been studied in both on static systems [12][13][14][15] and Floquet systems [16][17][18][19][20], whose properties can be captured by their effective static Hamiltonian. Most of the observed non-equilibrium long-lived behaviors [11,[21][22][23][24] are considered to be in the prethermal regime, which inspires a lot of interests in the search of the novel phases [7,10,16,[25][26][27]. Prethermal phases are generally featured by a quasi-stationary state with long-lived equilibrium-like properties [7,8,11,12,[28][29][30].Typically, these phases can exist in the interacting quantum systems with various symme- * These authors contributed equally.

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Prethermal quasiconserved observables in Floquet quantum systems

Cited by 18 publications

References 85 publications

Floquet prethermalization with lifetime exceeding 90s in a bulk hyperpolarized solid

Floquet prethermalization with lifetime exceeding 90s in a bulk hyperpolarized solid

Deep reinforcement learning for quantum Hamiltonian engineering

Floquet Prethermal Phase Protected by U(1) Symmetry on a Superconducting Quantum Processor

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