State Preparation on Quantum Computers via Quantum Steering

TL;DR

This paper introduces a measurement-induced quantum steering method for state preparation on digital quantum computers, enabling efficient initialization of qubits and qutrits, with potential applications in NISQ devices and quantum error correction.

Contribution

The authors demonstrate a novel state preparation protocol using measurement-induced steering with ancilla qubits, including active acceleration techniques, applicable to both qubits and qutrits.

Findings

Successfully prepared arbitrary qubit and qutrit states.

Active readout feedback accelerates state convergence.

Protocol incorporates essential operations like qubit reset and entangling circuits.

Abstract

One of the major components for realizing quantum computers is the ability to initialize the computer to a known fiducial state, also known as state preparation. We demonstrate a state preparation method via measurement-induced steering on contemporary, digital quantum computers. By delegating ancilla qubits and systems qubits, the system state is prepared by repeatedly performing the following steps: (1) executing a designated system-ancilla entangling circuit, (2) measuring the ancilla qubits, and (3) re-initializing ancilla qubits to known states through active reset. While the ancilla qubits are measured and reinitialized to known states, the system qubits are steered from arbitrary initial states to desired final states. We show results of the method by preparing arbitrary qubit states and qutrit (three-level) states. We also demonstrate that the state convergence can be accelerated by utilizing the readouts of the ancilla qubits to guide the protocol in an active manner. This protocol serves as a nontrivial example that incorporates and characterizes essential operations such as qubit reuse (qubit reset), entangling circuits, and measurement. These operations are not only vital for near-term noisy intermediate-scale quantum (NISQ) applications but are also crucial for realizing future error-correcting codes.