Generation and tomography of arbitrary optical qubits using transient collective atomic excitations

Area of Science:

• Quantum Information Science
• Atomic Physics
• Quantum Optics

Background:

• Quantum bits (qubits) are fundamental units of quantum information.
• Controlling qubit states is crucial for quantum computing and communication.
• Transient collective spin excitations offer a potential pathway for qubit generation.

Purpose of the Study:

• To demonstrate the preparation of heralded Fock-basis qubits.
• To achieve arbitrary control over qubit coefficients (amplitude and phase).
• To characterize the prepared qubit states.

Main Methods:

• Utilizing transient collective spin excitations in a hot atomic vapor.
• Employing a four-wave mixing process seeded by a weak coherent optical excitation.
• Using Raman-scattered photons as a heralding signal for qubit preparation.
• Performing balanced homodyne tomography for qubit state characterization.

Main Results:

• Successfully prepared heralded Fock-basis qubits in the form |a|0〉 + |b|1〉.
• Demonstrated arbitrary control over the qubit coefficients 'a' and 'b' via seed field manipulation.
• Verified the qubit state preparation and control using balanced homodyne tomography.

Conclusions:

• Heralded Fock-basis qubits can be reliably prepared from transient collective spin excitations.
• The demonstrated method allows for precise control over qubit properties.
• This technique is promising for advancing quantum information processing technologies.