研究目的
To develop and demonstrate a scalable entanglement metric based on multiple quantum coherences for verifying multipartite entanglement in near-term quantum devices.
研究成果
The study successfully demonstrates a scalable entanglement metric based on MQC, verifying 18-qubit multipartite GHZ entanglement on a superconducting device. The method is robust to noise and scalable, offering a practical approach for benchmarking near-term quantum devices.
研究不足
The circuit depth for generating N-qubit GHZ states scales as O(N), making the states fragile to decoherence. Simultaneous adjacent CX gates have lower fidelity due to ZZ interactions and cross-driving effects. Free evolution on idle qubits leads to unitary errors, and pulse alignment restrictions affect the effectiveness of π-pulses.
1：Experimental Design and Method Selection:
The experiment involves generating GHZ states on a 20-qubit superconducting device and verifying entanglement using multiple quantum coherences (MQC). The method is inspired by quantum sensing and involves applying collective rotations to the GHZ state and measuring the overlap between rotated and unrotated states.
2：Sample Selection and Data Sources:
The experiment uses a 20-qubit superconducting device with fixed frequency transmon qubits. Data is collected from the device's readout of the ground state population after applying the MQC protocol.
3：List of Experimental Equipment and Materials:
The primary equipment is the IBM Q System One, a 20-qubit superconducting quantum processor.
4：Experimental Procedures and Operational Workflow:
The protocol involves four steps: generating the GHZ state, applying a collective rotation, disentangling the GHZ state, and measuring the ground state population. The process is repeated for different rotation angles to extract MQC amplitudes.
5：Data Analysis Methods:
MQC amplitudes are extracted via discrete Fourier transform of the measured signal Sφ. The fidelity of the GHZ state is bounded using these amplitudes to verify multipartite entanglement.
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