Observation of classical-quantum crossover of 1/f flux noise and its paramagnetic temperature dependence

依赖于场的量子比特磁通噪声从材料特异性的磁性吸附物间无序交换相互作用模拟

Field-Dependent Qubit Flux Noise Simulated from Materials-Specific Disordered Exchange Interactions Between Paramagnetic Adsorbates

本研究通过材料特异性的磁性吸附物无序相互作用模拟，揭示了超导量子比特中磁通噪声的来源与抑制方法。

单个 Fe-triazole 自旋交叉纳米棒的氮空位磁测量

Nitrogen-vacancy magnetometry of individual Fe-triazole spin crossover nanorods

利用 NV 磁显微镜结合 SEM 与拉曼表征，研究 20–1000 nm Fe-triazole 纳米颗粒及单个纳米棒的 LS 态磁性，发现多数纳米棒呈轻微顺磁性。

Metastability in an open quantum Ising model

We apply a recently developed theory for metastability in open quantum systems to a one-dimensional dissipative quantum Ising model. Earlier results suggest this model features either a non-equilibrium phase transition or a smooth but sharp crossover, where the stationary state changes from paramagnetic to ferromagnetic, accompanied by strongly intermittent emission dynamics characteristic of first-order coexistence between dynamical phases. We show that for a range of parameters close to this transition/crossover point the dynamics of the finite system displays pronounced metastability, i.e.,…

Coherent control of artificial molecules using an Aharonov-Bohm magnetic flux

Bonding and anti-bonding states of artificial molecules have been realized in experiments by directly coupling two quantum dots. Without a direct coupling between two nearby quantum dots, here we show that a continuous crossover, from symmetric to anti-symmetric molecular state, can be achieved by changing the flux through a double quantum dot Aharonov-Bohm (AB) interferometer. We explicitly present the flux-dependent real-time processes of molecular-state formation. In contrast to the transport current, which has a $2π$ period, the quantum state of the DQD molecule has a $4π$ period in the AB…

Direct identification of dilute surface spins on Al$_2$O$_3$: Origin of flux noise in quantum circuits

It is universally accepted that noise and decoherence affecting the performance of superconducting quantum circuits are consistent with the presence of spurious two-level systems (TLS). In recent years bulk defects have been generally ruled out as the dominant source, and the search has focused on surfaces and interfaces. Despite a wide range of theoretical models and experimental efforts, the origin of these surface TLS still remains largely unknown, making further mitigation of TLS induced decoherence extremely challenging. Here we use a recently developed on-chip electron spin resonance (ES…

Observation of the Crossover from Photon Ordering to Delocalization in Tunably Coupled Resonators

Networks of nonlinear resonators offer intriguing perspectives as quantum simulators for non-equilibrium many-body phases of driven-dissipative systems. Here, we employ photon correlation measurements to study the radiation fields emitted from a system of two superconducting resonators, coupled nonlinearly by a superconducting quantum interference device (SQUID). We apply a parametrically modulated magnetic flux to control the linear photon hopping rate between the two resonators and its ratio with the cross-Kerr rate. When increasing the hopping rate, we observe a crossover from an ordered to…