Steering the evolution of single spin systems is crucial for quantum computing and quantum sensing. The dynamics of quantum systems has been theoretically investigated with parity-time-symmetric ...Hamiltonians exhibiting exotic properties. Although parity-time symmetry has been explored in classical systems, its observation in a single quantum system remains elusive. We developed a method to dilate a general parity-time-symmetric Hamiltonian into a Hermitian one. The quantum state evolutions ranging from regions of unbroken to broken Formula: see text symmetry have been observed with a single nitrogen-vacancy center in diamond. Owing to the universality of the dilation method, our result provides a route for further exploiting and understanding the exotic properties of parity-time symmetric Hamiltonian in quantum systems.
Hawking radiation is one of the most intriguing and elusive predictions of quantum field theory in curved spacetime. Previous works simulating Hawking radiation have been mostly based on Unruh’s ...scenario, where the propagation of quantum field in classical gravitational background is mimicked. Here, guided by the duality between black holes in Jackiw-Teitelboim (JT) dilaton gravity and solitons in sine-Gordon (SG) field theory, we propose the use of a superconducting circuit for investigating analogue Hawking radiation.
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+
1
dimensional black holes can be realized as solitons of the SG equation of superconducting phase. It is found despite the absence of field theoretic dynamical modes, the analogue Hawking radiation is emitted in terms of the quantum soliton evaporation as a result of quantum perturbation of the black hole metric. Our theoretical proposal could not only facilitate the observation of relativistic quantum effects in lab, but also contribute to experimentally exploring the quantum mechanics of solitons, especially to the deep relationship between such mechanics and black hole physics.
Abstract
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
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2
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.
The Lyapunov exponent of a quantum system has been predicted to be bounded by
λ
L
≤
2
π
T
/
ħ
, where
T
is its temperature, as established by Maldacena, Shenker, and Stanford (MSS). This bound plays ...an important role in studying very diverse topics of physics, ranging from the dynamics of interacting many-body systems to the black hole information problem, and it is saturated when the system under consideration is the exact holographic dual of a black hole. Based on the fact that an inverted harmonic oscillator (IHO) may exhibit the behavior of thermal energy emission, in close analogy to the Hawking radiation emitted by black holes, we propose using a trapped ion as an implementation of the IHO to verify, in a concrete analogue-gravity system, whether the MSS bound can be identically saturated. To this end, we provide prescriptions for experimentally observing the scattering process at the IHO potential, which yields an analogue of Hawking radiation, as well as for how to measure the corresponding out-of-time-ordered correlation function (OTOC), diagnosing quantum chaos, in this thermally excited semiclassical system. We theoretically show, for an experimentally realizable analogue-gravity setup, that the effective Hawking temperature of the trapped-ion-IHO indeed matches the upper MSS bound for the speed of scrambling.
Reactive oxygen species (ROS) play an essential role in physiological and pathological processes. Studies on the regulation of ROS for disease treatments have caused wide concern, mainly involving ...the topics in ROS‐regulating therapy such as antioxidant therapy triggered by ROS scavengers and ROS‐induced toxic therapy mediated by ROS‐elevation agents. Benefiting from the remarkable advances of nanotechnology, a large number of nanomaterials with the ROS‐regulating ability are developed to seek new and effective ROS‐related nanotherapeutic modalities or nanomedicines. Although considerable achievements have been made in ROS‐based nanomedicines for disease treatments, some fundamental but key questions such as the rational design principle for ROS‐related nanomaterials are held in low regard. Here, the design principle can serve as the initial framework for scientists and technicians to design and optimize the ROS‐regulating nanomedicines, thereby minimizing the gap of nanomedicines for biomedical application during the design stage. Herein, an overview of the current progress of ROS‐associated nanomedicines in disease treatments is summarized. And then, by particularly addressing these known strategies in ROS‐associated therapy, several fundamental and key principles for the design of ROS‐associated nanomedicines are presented. Finally, future perspectives are also discussed in depth for the development of ROS‐associated nanomedicines.
Reactive Oxygen Species (ROS)‐regulating nanomedicines for disease treatments mainly include ROS‐upregulating nanomedicines and ROS‐downregulating nanomedicines. Here, ROS‐upregulating nanomedicines can exert the toxic effect by employing nanoplatforms to enhance ROS generation in pathological sites for ROS‐induced toxic therapy, and ROS‐downregulating nanomedicines can scavenge excess ROS to maintain normal physiological process and avoid oxidative stress injuries for antioxidant therapy.
High fidelity single-shot readout of qubits is a crucial component for fault-tolerant quantum computing and scalable quantum networks. In recent years, the nitrogen-vacancy (NV) center in diamond has ...risen as a leading platform for the above applications. The current single-shot readout of the NV electron spin relies on resonance fluorescence method at cryogenic temperature. However, the spin-flip process interrupts the optical cycling transition, therefore, limits the readout fidelity. Here, we introduce a spin-to-charge conversion method assisted by near-infrared (NIR) light to suppress the spin-flip error. This method leverages high spin-selectivity of cryogenic resonance excitation and flexibility of photoionization. We achieve an overall fidelity > 95% for the single-shot readout of an NV center electron spin in the presence of high strain and fast spin-flip process. With further improvements, this technique has the potential to achieve spin readout fidelity exceeding the fault-tolerant threshold, and may also find applications on integrated optoelectronic devices.
High-fidelity projective readout of a qubit's state in a single experimental repetition is a prerequisite for various quantum protocols of sensing and computing. Achieving single-shot readout is ...challenging for solid-state qubits. For Nitrogen-Vacancy (NV) centers in diamond, it has been realized using nuclear memories or resonant excitation at cryogenic temperature. All of these existing approaches have stringent experimental demands. In particular, they require a high efficiency of photon collection, such as immersion optics or all-diamond micro-optics. For some of the most relevant applications, such as shallow implanted NV centers in a cryogenic environment, these tools are unavailable. Here we demonstrate an all-optical spin readout scheme that achieves single-shot fidelity even if photon collection is poor (delivering less than 10
clicks/second). The scheme is based on spin-dependent resonant excitation at cryogenic temperature combined with spin-to-charge conversion, mapping the fragile electron spin states to the stable charge states. We prove this technique to work on shallow implanted NV centers, as they are required for sensing and scalable NV-based quantum registers.
The exceptional point, known as the non-Hermitian degeneracy, has special topological structure, leading to various counterintuitive phenomena and novel applications, which are refreshing our ...cognition of quantum physics. One particularly intriguing behavior is the mode switch phenomenon induced by dynamically encircling an exceptional point in the parameter space. While these mode switches have been explored in classical systems, the experimental investigation in the quantum regime remains elusive due to the difficulty of constructing time-dependent non-Hermitian Hamiltonians in a real quantum system. Here we experimentally demonstrate dynamically encircling the exceptional point with a single nitrogen-vacancy center in diamond. The time-dependent non-Hermitian Hamiltonians are realized utilizing a dilation method. Both the asymmetric and symmetric mode switches have been observed. Our Letter reveals the topological structure of the exceptional point and paves the way to comprehensively explore the exotic properties of non-Hermitian Hamiltonians in the quantum regime.
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