Realization of dark state in a three-dimensional transmon superconducting qutrit

Abstract

We realize the dark state in a three-dimensional transmon superconducting qutrit that consists of three cascading energy levels: |0⟩, |1⟩, and |2⟩. When the system is simultaneously driven with two tone microwaves on resonance with |0⟩, |1⟩ and |1⟩, |2⟩, respectively, it is found that the state of the system will generally evolve in time domain. However, the qutrit state is frozen-out if it is initialized in a dark state for corresponding drive amplitudes. We observe this freeze-out phenomenon by changing the amplitude of the microwaves while fixing the initial state or vice versa.

Superadiabatic population transfer in a three-level superconducting circuit

“…Here we demonstrate a superadiabatic protocol in the microwave regime using circuit quantum electrodynamics as the experimental platform (26). This is an important task in quantum control, where efficient and fast state preparation is needed as an initial step for many algorithms (27,28). Our experiment employs a superconducting transmon circuit (29), where the first three states are addressed by microwave fields with the goal of populating the second excited state, while starting from the ground state and without populating the first excited state.…”

“…We use the first three states of a superconducting transmon circuit (27) to transfer population between the ground state and the second excited state. This is an important task in quantum control of multilevel systems, where fast and efficient state preparation serves as an initial step for many algorithms (28,29). We achieve this by using three microwave pulses: Two of them realize the stimulated Raman adiabatic passage (STIRAP) (30)(31)(32), while the third is a two-photon process creating the counterdiabatic Hamiltonian, which forces the system to follow its instantaneous eigenstate even though the adiabatic condition is violated.…”

Unified generation and fast emission of arbitrary single-photon multimode $W$ states

“…In this paper, we present a unified scheme to generate arbitrary single-photon multimode W states |W N , satisfying the aforementioned requirements. We have a qutrit [36] (e.g., a Λ type superconducting quantum interference device (SQUID) [37,38], transmon [39][40][41] or an xmon [42]) driven by pump-laser pulses and coupled to N spatially separated resonators, to obtain |W N Eq. (1) with A i just proportional to the coupling strength between the i-th cavity mode and the qutrit, g i .…”

Fabrication of Al/AlO x /Al junctions using pre-exposure technique at 30-keV e-beam voltage

“…Owing to its long coherence time and simple fabrication process, the Al/AlO x /Al junction is used by many SQC groups nowadays. [6][7][8][9][10][11][12][13][14] Among different kinds of fabrication processes of the aluminum junction, the Dolan bridge technique is widely adopted because it only needs one lithographic patterning step [15] in which a suspended bridge is formed via a different clearing dose of the bilayer resist. After two-angle aluminum film depositions and an in-situ oxidation in electron beam evaporator, the Al/AlO x /Al junction is prepared.…”