Detection of Quantum Critical Points by a Probe Qubit

Zhang, Jingfu; Peng, Xinhua; Rajendran, Nageswaran; Suter, Dieter

doi:10.1103/physrevlett.100.100501

Cited by 105 publications

(89 citation statements)

References 31 publications

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“…Alternatively, fidelity susceptibility can also be obtained from the overlap of quantum many-body wave functions, which has been measured in a NMR quantum simulator [96] and, notably, in ultracold bosons by utilizing a quantum gas microscope [97]. Combining these detection approaches with recent efforts of realizing Kondo physics in ultracold atomic gases [19][20][21][22], the proposed diagnostic The data are the same as in Fig.…”

Section: H Y S I C a L R E V I E W L E T T E R S Week Ending 4 Decembmentioning

confidence: 99%

Fidelity Susceptibility Perspective on the Kondo Effect and Impurity Quantum Phase Transitions

2015

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The Kondo effect is a ubiquitous phenomenon appearing at low temperature in quantum confined systems coupled to a continuous bath. Efforts in understanding and controlling it have triggered important developments across several disciplines of condensed matter physics. A recurring pattern in these studies is that the suppression of the Kondo effect often results in intriguing physical phenomena such as impurity quantum phase transitions or non-Fermi-liquid behavior. We show that the fidelity susceptibility is a sensitive indicator for such phenomena because it quantifies the sensitivity of the system's state with respect to its coupling to the bath. We demonstrate the power of the fidelity susceptibility approach by using it to identify the crossover and quantum phase transitions in the one and two impurity Anderson models. The feasibility of measuring fidelity susceptibility in condensed matter as well as ultracold quantum gases experiments opens exciting new routes to diagnose the Kondo problem and impurity quantum phase transitions. [7,8], and boundary conformal field theory [9] to the quantum impurity problems. Experimental interest increased in the late 1990s due to breakthroughs in fabricating artificial nanodevices [10][11][12][13][14][15]. Kondo physics is also directly relevant to dissipative two-state systems [16] and the heavy-fermion compounds [17,18]. There has also been an increasing interest in realizing the Kondo effect in ultracold atomic gases [19][20][21][22]. High controllability of the latter system may offer chances to gain even deeper understandings of the intriguing physics of quantum impurity models.A general description of the quantum impurity problems can be written aŝ HðλÞ ¼Ĥ impurity þĤ bath |fflfflfflfflfflfflfflfflfflfflffl ffl{zfflfflfflfflfflfflfflfflfflfflffl ffl}whereĤ 0 describes the quantum impurity together with a continuous bath, and the last term describes the coupling between them. We treat λ as a parameter and aim to characterize the state of the quantum impurity as a function of its coupling to the bath. The Kondo effect originates from the bath's tendency to screen the local moment formed on the quantum impurity. Renormalization group analysis shows that, in the Kondo region, the coupling strength flows to infinity at low energy [4,5], implying that the local moment will eventually get screened at a low enough temperature even with an arbitrarily weak bare impurity-bath coupling strength. There are, however, various physical processes that can compete with the Kondo effect. In the presence of such competitions, the system may undergo an impurity quantum phase transition where a competing state (local moment, charge order, etc.) takes over as the bath-impurity coupling λ decreases. Suppression of the Kondo screening often leads to non-Fermi liquid behavior [23,24]. However, different from the quantum phase transition in bulk systems [25], at such an impurity quantum critical point, only a nonextensive term in the free energy becomes singular. It is not always straightfo...

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Section: H Y S I C a L R E V I E W L E T T E R S Week Ending 4 Decembmentioning

confidence: 99%

Fidelity Susceptibility Perspective on the Kondo Effect and Impurity Quantum Phase Transitions

2015

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“…This coupling competes with the Zeeman energy being proportional to the geomagnetic field, and leads to a QPT at the critical point λ = 1. A central spin uniformly coupled with each spin in this TFI system possesses the dynamic sensitivity described by the sharp decay of LE near the QPT [22], which has been experimentally verified [20,23,24].…”

Section: Fig 1: (Color Online)mentioning

confidence: 67%

“…But the experiments [20,23,24] however demonstrated that even for N = 2, there still exists the dynamic sensitivity induced by quantum criticality. This result implies that dynamic sensitivity may have a close relation with the level crossing.…”

Section: Fig 1: (Color Online)mentioning

confidence: 99%

Sensitive chemical compass assisted by quantum criticality

Cai

Ai²,

Quan³

et al. 2012

Phys. Rev. A

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The radical-pair-based chemical reaction could be used by birds for the navigation via the geomagnetic direction. An inherent physical mechanism is that the quantum coherent transition from a singlet state to triplet states of the radical pair could response to the weak magnetic field and be sensitive to the direction of such a field and then results in different photopigments in the avian eyes to be sensed. Here, we propose a quantum bionic setup for the ultra-sensitive probe of a weak magnetic field based on the quantum phase transition of the environments of the two electrons in the radical pair. We prove that the yield of the chemical products via the recombination from the singlet state is determined by the Loschmidt echo of the environments with interacting nuclear spins. Thus quantum criticality of environments could enhance the sensitivity of the detection of the weak magnetic field. Introduction.-Since Schrödinger questioned "what is life" from the general point view of a quantum physicist [1], scientists have never stopped the long-term exploration for the physical sources of the living phenomena, and this even stimulated the enthusiasm for the great discovery of the DNA genetic molecule [2]. Today it seems trivial to say that the life is of quantum for the molecules composing lives obey quantum laws, but some recent discoveries are very intriguing as some optimized living processes may be based on the nontrivial quantum effect from quantum coherence. One example in point is the photosynthesis process. Recent experiments have been able to exactly determine the time scales of various transfer processes by the 2D optical spectroscopy, and then show quantum coherence effects in energy transfer via collective excitations of some light-harvesting complexes [3][4][5].

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“…Recent investigations show that the LE may be employed to characterize QPTs since it has been found to have extra-fast decay in the vicinity of the critical points [42,[50][51][52][53][54]. Furthermore, as shown in Refs.…”

Section: Lochmidt Echo and Fidelity For The Dicke Model At Qptmentioning

confidence: 99%

Complexity and instability of quantum motion near a quantum phase transition

et al. 2014

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We show that the number of harmonics of the Wigner function, recently proposed as a measure of quantum complexity, can also be used to characterize quantum phase transitions. The non-analytic behavior of this quantity in the neighborhood of a quantum phase transition is illustrated by means of the Dicke model and is compared to two well-known measures of the (in)stability of quantum motion: the quantum Loschmidt echo and fidelity.

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Detection of Quantum Critical Points by a Probe Qubit

Cited by 105 publications

References 31 publications

Fidelity Susceptibility Perspective on the Kondo Effect and Impurity Quantum Phase Transitions

Fidelity Susceptibility Perspective on the Kondo Effect and Impurity Quantum Phase Transitions

Sensitive chemical compass assisted by quantum criticality

Complexity and instability of quantum motion near a quantum phase transition

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