Tuned transition from quantum to classical for macroscopic quantum states

Abstract

The boundary between the classical and quantum worlds has been intensely studied. It remains fascinating to explore how far the quantum concept can reach with use of specially fabricated elements. Here we employ a tunable flux qubit with basis states having persistent currents of 1$\mu$A carried by a billion electrons. By tuning the tunnel barrier between these states we see a cross-over from quantum to classical. Released from non-equilibrium, the system exhibits spontaneous coherent oscillations. For high barriers the lifetime of the states increases dramatically while the tunneling period approaches the phase coherence time and the classical regime is reached.

4 pages, 5 figures

References in corpus (10)

• Coherent control of macroscopic quantum states in a single-Cooper-pair box
• Experimental violation of a Bell's inequality in time with weak measurement
• Dephasing of a superconducting qubit induced by photon noise
• Tuning the Gap of a Superconducting Flux Qubit
• Microwave-Induced Cooling of a Superconducting Qubit
• Sisyphus cooling and amplification by a superconducting qubit
• Simple Phase Bias for Superconducting Circuits
• Possible implementation of adiabatic quantum algorithm with superconducting flux qubits
• Coherent oscillations in a superconducting tunable flux qubit manipulated without microwaves
• The size of macroscopic superposition states in flux qubits

Cited by in corpus (14)

• Ultrastrong coupling of a single artificial atom to an electromagnetic continuum in the nonperturbative regime
• Experimental realization of an intrinsically error-protected superconducting qubit
• Moving beyond the transmon: Noise-protected superconducting quantum circuits
• Generating nonclassical photon-states via longitudinal couplings between superconducting qubits and microwave fields
• Gradiometric flux qubits with tunable gap
• Steady-state nested entanglement structures in harmonic chains with single-site squeezing manipulation
• Quantum interferometry with a g-factor-tunable spin qubit
• Mechanism of generation of a Josephson phase shift by an Abrikosov vortex
• Tunable coupling between three qubits as a building block for a superconducting quantum computer
• Simulating long-distance entanglement in quantum spin chains by superconducting flux qubits
• Controlling the energy gap of a tunable two-level system by ac drive
• Coherent errors in stabilizer codes caused by quasistatic phase damping
• A tunable macroscopic quantum system based on two fractional vortices
• Current biased gradiometric flux qubit in a circuit-QED architecture