# SQUBIT-2 Sintesi della relazione

Project ID:
IST-2001-39083

Finanziato nell'ambito di:
FP5-IST

Paese:
Netherlands

## Coherent dynamics of a flux qubit coupled to a harmonic oscillator

TU Delft has fabricated and investigated a system of a flux qubit coupled to a harmonic oscillator, observing Rabi oscillations of the composite system. The qubit is the standard TU Delft three Josephson junction flux qubit, and the harmonic oscillator is a DC SQUID with attached capacitor. The potential for this scheme is very large, providing a strongly local system with controlled locality. In this respect it strongly differs from the approach taken by others (e.g. Yale), where the harmonic oscillator has to be taken of a size comparable to the wavelength associated with the qubit level splitting frequency.

The actual implementation employs the SQUID in two distinctly different manners: as the detecor (as usual), and as the harmonic oscillator (which makes the system to be a composite one). The SQUID with the capacitor attached to it, may act quantum mechanically. This requires the level separation (or plasma frequency) to be sufficiently large, and the damping to be sufficiently small, such that the decay rate is smaller than the energy of the qubit-SQUID coupling.

The results imply successful entanglement of a 2-level qubit and an n-level harmonic oscillator, demonstrating for the first time the quantum dynamics of a solid state two-component system through controlled and conditional Rabi flopping employing the lowest four levels of the composite system.

The actual implementation employs the SQUID in two distinctly different manners: as the detecor (as usual), and as the harmonic oscillator (which makes the system to be a composite one). The SQUID with the capacitor attached to it, may act quantum mechanically. This requires the level separation (or plasma frequency) to be sufficiently large, and the damping to be sufficiently small, such that the decay rate is smaller than the energy of the qubit-SQUID coupling.

The results imply successful entanglement of a 2-level qubit and an n-level harmonic oscillator, demonstrating for the first time the quantum dynamics of a solid state two-component system through controlled and conditional Rabi flopping employing the lowest four levels of the composite system.