Quantum physics has been applied to study problems in computing complexity in recent years, which has become a new frontier in computer science. Computer hardware that is operated according to the laws of quantum mechanics can realize novel quantum protocols and bring enormous speed-up for certain computationally hard problems. The key issue in implementing such hardware is in achieving highly accurate and fast control on the quantum logic elements so that they can beat the hazardous effects from the environmental noise. For solid-state quantum processors, including superconducting systems and semiconductor systems, such control is usually achieved via adjustable local parameters, where careful designing of the circuit and the connections to external sources are required. In this project, a quantum global mode will be exploited to achieve efficient implementation of the quantum protocols. Here, the quantum global mode is the microwave photon mode in a nanoscale quantum resonator that has millimeter wavelength, can couple with multiple quantum logic elements simultaneously, and has demonstrated microsecond quantum coherence times. Meanwhile, the global mode will also be considered as a probe to measure quantum entanglement and quantum coherence effects in the solid-state quantum processors. Two questions will be studied in this project. First, solid-state quantum simulators that can emulate quantum many-body systems involving arrays of solid-state elements will be studied, where the global quantum mode will act as a control as well as a detector of the quantum phase transitions in the simulators. Second, a universal quantum computer of spurious two-level fluctuators in the superconducting system will be studied where the global mode can provide individual control, effective coupling, and readout of the fluctuator states. Both the hardware aspect and the software aspect will be investigated.
