论文标题
多级超导码位的自旋 - 玻色子量子相变
Spin-boson quantum phase transition in multilevel superconducting qubits
论文作者
论文摘要
当前，超导电路是作为探索多体物理学的多功能平台开发的，它是建立在通常被视为两级量子位的非线性元素上的。一个经典的示例是由电荷量子量耦合到传输线的，这导致了量子耗散的著名自旋 - 玻璃孔描述。我们表明，超导码头的固有多级结构极大地限制了由于相位定位而引起的自旋 - 玻色子范式的有效性，从而将波函数扩散到许多电荷状态下。数值重新归一化组模拟还表明，量子临界点从多层次制度中的物理可访问范围移出。在简单的变分状态下，对这些多级效果的征收离散性，这些效果与大型设备有关。
Superconducting circuits are currently developed as a versatile platform for the exploration of many-body physics, by building on non-linear elements that are often idealized as two-level qubits. A classic example is given by a charge qubit that is capacitively coupled to a transmission line, which leads to the celebrated spin-boson description of quantum dissipation. We show that the intrinsic multilevel structure of superconducting qubits drastically restricts the validity of the spin-boson paradigm due to phase localization, which spreads the wavefunction over many charge states. Numerical Renormalization Group simulations also show that the quantum critical point moves out of the physically accessible range in the multilevel regime. Imposing charge discreteness in a simple variational state accounts for these multilevel effects, that are relevant for a large class of devices.
