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Entangled macroscopic quantum States in two superconducting qubits
1Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742, USA. berkley@physics.umd.edu
Science (New York, N.Y.)
|May 17, 2003
Summary
Researchers created entangled macroscopic quantum states in two Josephson-junction qubits. This demonstrates entanglement over a 0.7-millimeter distance, controlled by bias currents and confirmed by microwave spectroscopy.
Area of Science:
- Quantum physics
- Superconducting circuits
Background:
- Josephson-junction qubits are fundamental units in quantum computing.
- Controlling interactions between qubits is crucial for creating entangled states.
Purpose of the Study:
- To demonstrate the creation of entangled macroscopic quantum states in coupled Josephson-junction qubits.
- To investigate the control of qubit interactions using bias currents.
Main Methods:
- Utilized two current-biased Josephson-junction qubits coupled via a capacitor.
- Employed microwave spectroscopy (4-6 GHz) at 20 millikelvin to probe energy levels.
- Varied individual junction bias currents to control qubit interactions and resonance.
Main Results:
- Spectroscopic evidence confirmed the creation of entangled macroscopic quantum states.
- Observed energy levels closely matched theoretical predictions for entangled states.
- Entangled states were sustained over a spatial separation of 0.7 millimeters between qubits.
Conclusions:
- Successfully demonstrated entanglement in spatially separated macroscopic quantum systems.
- Bias current control offers a viable method for tuning qubit interactions and achieving entanglement.
- The findings support the scalability of superconducting qubits for quantum information processing.
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