Coherence and Rydberg Blockade of Atomic Ensemble Qubits.

Area of Science:

• Quantum information science
• Atomic physics
• Ensemble quantum computing

Background:

• Quantum computing relies on robust qubits.
• Multiatom ensembles offer a scalable approach to qubit realization.
• Controlling interactions between atomic ensembles is crucial for quantum operations.

Purpose of the Study:

• To demonstrate the encoding of multiatom ensemble qubits using the |W⟩ state.
• To investigate the coherence times and Rydberg blockade effects in these systems.
• To assess the potential for deterministic entanglement of atomic ensembles.

Main Methods:

• Utilizing optically trapped Rubidium (Rb) atoms.
• Encoding quantum information in the |W⟩ state of multiatom ensembles.
• Measuring coherence times (T2) and Rydberg blockade fidelity.

Main Results:

• Achieved a T2 coherence time of 2.6(3) ms for an average of 7.6 atoms, inversely scaling with atom number.
• Demonstrated strong Rydberg blockade between two ensemble qubits with 0.89(1) fidelity.
• Obtained near-perfect fidelity (~1.0) for Rydberg blockade when postselected on control ensemble excitation.

Conclusions:

• The |W⟩ state encoding is effective for multiatom ensemble qubits.
• Rydberg blockade in these systems is strong and controllable.
• These findings represent significant progress towards deterministic entanglement of atomic ensembles.