Tunable quantum beam splitters for coherent manipulation of a solid-state tripartite qubit system

Abstract

Coherent control of quantum states is at the heart of implementing solid-state quantum processors and testing quantum mechanics at the macroscopic level. Despite significant progress made in recent years in controlling single- and bi-partite quantum systems, coherent control of quantum wave function in multipartite systems involving artificial solid-state qubits has been hampered due to the relatively short decoherence time and lack of precise control methods. Here we report the creation and coherent manipulation of quantum states in a tripartite quantum system, which is formed by a superconducting qubit coupled to two microscopic two-level systems (TLSs). The avoided crossings in the system's energy-level spectrum due to the qubit–TLS interaction act as tunable quantum beam splitters of wave functions. Our result shows that the Landau–Zener–Stückelberg interference has great potential in precise control of the quantum states in the tripartite system.

Amplitude spectroscopy of two coupled qubits

“…In the language of wave functions, an interference of different zone states, predicted by Stückelberg 11 is possible. As applied to qubits these effects have lately been discussed in numerous works [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] .…”

Rapid characterization of microscopic two-level systems using Landau-Zener transitions in a superconducting qubit

“…20,21 With this traditional method, the coupling between a TLS and a qubit results in an anti-crossing (or energy level splitting) on spectroscopy. 5,6,18,19,22,23 However, the visibility of the anti-crossing depends on the width of the resonant peak as well as the measurement resolution. 24 Timeconsuming high resolution spectroscopy measurement hinders the investigation of the dynamic evolution of TLSs in solid-state devices.…”

“…23,25,26 When initialized in the ground state, it will be excited to the excited state by absorbing resonant microwave photons. A transition peak with width dependent on the decoherence time can be observed.…”

Quantum interference in the field ionization of Rydberg atoms

“…In solid-state physics, LZ transitions have been used as a beam splitter for manipulating a superconducting qubit with MachZehnder interferometry [20], for coherent control of a qubit system [21], and again as a beam splitter for electronic spin states [22]. They have been used to develop quantum memory in diamond nitrogen-vacancy centers [23].…”