Observation of a quantum phase transition in the quantum Rabi model with a single trapped ion

Cai, Meihan; Liu, Z.-D.; Zhao, Wending; Wu, Yukai; Mei, Quanxin; Jiang, Yubao; He, Longfei; Zhang, X.; Zhou, Z.-C.; Duan, Liwei

doi:10.1038/s41467-021-21425-8

Cited by 133 publications

(89 citation statements)

References 64 publications

(37 reference statements)

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“…Finite-size scaling.-Physically, this last case is more challenging, since we need two noncommuting discrete symmetries, Π and Ĉ, to build a complete description of thermodynamic equilibrium. Hence, we work with α ¼ 0, which has been the object of recent experimental works [71,72], to perform a stringent test on our conjecture. As explained above, it implies energy doublets jE n;þ − E n;− j ¼ 0, and also…”

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confidence: 99%

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Constant of Motion Identifying Excited-State Quantum Phases

Corps

Relaño

2021

Phys. Rev. Lett.

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We propose that a broad class of excited-state quantum phase transitions (ESQPTs) gives rise to two different excited-state quantum phases. These phases are identified by means of an operator Ĉ, which is a constant of motion in only one of them. Hence, the ESQPT critical energy splits the spectrum into one phase where the equilibrium expectation values of physical observables crucially depend on this constant of motion and another phase where the energy is the only relevant thermodynamic magnitude. The trademark feature of this operator is that it has two different eigenvalues AE1, and, therefore, it acts as a discrete symmetry in the first of these two phases. This scenario is observed in systems with and without an additional discrete symmetry; in the first case, Ĉ explains the change from degenerate doublets to nondegenerate eigenlevels upon crossing the critical line. We present stringent numerical evidence in the Rabi and Dicke models, suggesting that this result is exact in the thermodynamic limit, with finite-size corrections that decrease as a power law.

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confidence: 99%

“…Further research is needed to determine how to link our results with typical features of standard phase transitions, like critical slowing down. Experimental tests involving broken-symmetry equilibrium states [71,72] will play a relevant role in this endeavor.…”

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confidence: 99%

Constant of Motion Identifying Excited-State Quantum Phases

Corps

Relaño

2021

Phys. Rev. Lett.

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“…Such finite size quantum phase transition was discussed in the context of the quantum Rabi model [11], where the dimensionless parameter η qr = ω/Ω is introduced. In the limit η qr → 0, the quantum Rabi model exhibits a phase transition, which was recently experimentally observed [12]. Here, one can define the ratio η pm = ω/Φ such that, in the limit η pm → 0, the periodically driven quantum JT system exhibits critical behavior at λ c = 1.…”

Section: Quantum Metrology With Periodic Modulating Quantum System: Coherent Evolutionmentioning

confidence: 65%

“…Usually, the existence of the quantum phase transition requires a thermodynamic limit, where the number of constituents goes to infinity. A different class of phase transitions was introduced in an interacting system of single-mode cavity field and two-level atom, where the thermodynamic limit requires the cavity frequency in units of atomic transition frequency to tend to zero [11,12]. An enhanced parameter estimation was proposed with such finite size critical quantum optical system for high-precision force measurements [13][14][15] or frequency measurements [8,9].…”

Section: Introductionmentioning

confidence: 99%

Enhanced Parameter Estimation with Periodically Driven Quantum Probe

Ivanov

2021

Entropy

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I propose a quantum metrology protocol for measuring frequencies and weak forces based on a periodic modulating quantum Jahn–Teller system composed of a single spin and two bosonic modes. I show that, in the first order of the frequency drive, the time-independent effective Hamiltonian describes spin-dependent interaction between the two bosonic modes. In the limit of high-frequency drive and low bosonic frequency, the quantum Jahn–Teller system exhibits critical behavior which can be used for high-precision quantum estimation. A major advantage of the scheme is the robustness of the system against spin decoherence, which allows it to perform parameter estimation with measurement time not limited by spin dephasing.

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“…For example, the dynamics of QRM [24][25][26] and nonequilibrium SPT of Dicke model have been experimentally simulated on various quantum simulation platforms, e.g., Bose-Einstein condensates [27][28][29] and trapped ions 30 . Very recently, the quantum phase transition of the standard QRM has been simulated with trapped ions 31 . However, the effect of the no-go theorem has not been experimentally studied so far.…”

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confidence: 99%

Experimental quantum simulation of superradiant phase transition beyond no-go theorem via antisqueezing

Chen

Jiang

et al. 2021

Nat Commun

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The superradiant phase transition in thermal equilibrium is a fundamental concept bridging statistical physics and electrodynamics, which has never been observed in real physical systems since the first proposal in the 1970s. The existence of this phase transition in cavity quantum electrodynamics systems is still subject of ongoing debates due to the no-go theorem induced by the so-called A2 term. Moreover, experimental conditions to study this phase transition are hard to achieve with current accessible technology. Based on the platform of nuclear magnetic resonance, here we experimentally simulate the occurrence of an equilibrium superradiant phase transition beyond no-go theorem by introducing the antisqueezing effect. The mechanism relies on that the antisqueezing effect recovers the singularity of the ground state via exponentially enhancing the zero point fluctuation of system. The strongly entangled and squeezed Schrödinger cat states of spins are achieved experimentally in the superradiant phase, which may play an important role in fundamental tests of quantum theory and implementations of quantum metrology.

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Observation of a quantum phase transition in the quantum Rabi model with a single trapped ion

Cited by 133 publications

References 64 publications

Constant of Motion Identifying Excited-State Quantum Phases

Constant of Motion Identifying Excited-State Quantum Phases

Enhanced Parameter Estimation with Periodically Driven Quantum Probe

Experimental quantum simulation of superradiant phase transition beyond no-go theorem via antisqueezing

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