Mermin's inequalities of multiple qubits with orthogonal measurements onIBMQ 53‐qubit system

Abstract

Summary Entanglement properties of IBM Q 53‐qubit quantum computer are carefully examined with the noisy intermediate‐scale quantum technology. We study Greenberger‐Horne‐Zeilinger‐like states with multiple qubits (N = 2 to N = 7) on IBM Rochester and compare their maximal violation values of Mermin's polynomials with analytic results. A rule of N‐qubits orthogonal measurements is taken to further justify the entanglement less than maximal values of local realism. The orthogonality of measurements is another reliable criterion for entanglement except the maximal values of LR. Our results indicate that the entanglement of IBM 53 qubits is reasonably good when N ≤ 4, while for the longer entangle chains, the entanglement is only valid for some special connectivity.

Phase Analysis on the Error Scaling of Entangled Qubits in a 53-Qubit System

“…From previous reported results 18 for the IBM Rochester 19 , entanglement of a large number of qubits are easily affected by the environmental noise, but the entanglement states of a small number of qubits are relatively stable 18 . Also, our measurements provide another easy test for the entanglement of a N-qubit system 18 . Generally, a 2-qubit pair uses Bell's 20 or Mermin's inequality 7 to distinguish its "quantum-ness" from local realism (LR).…”

“…Although the phase angles tested for the maximum values of LR are different, the basic physics for both are similardifference lies only in the superposition of the subsystem quantum states. For multiple qubits, maximal values of Mermin's polynomials are often relied upon to understand the entanglement physics of a N-qubit system and its quantum subsystems 18 . However, transitions between states can occur if the energy levels of the NISQ 24 system fluctuate (Supplement A).…”

Phase analysis on the error scaling of entangled qubits in a 53-qubit system

“…The use of entanglement in communication 17 , computing 18 and quantum radar 19 is a very active area of research and development. From previous reported results 20 for the IBM Rochester 21 , entanglement of a large number of qubits are easily affected by the environmental noise, but the entanglement states of a small number of qubits are relatively stable 20 . Also, our measurements provide another easy test for the entanglement of a N-qubit system 20 .…”

Dissipative engineering of a tripartite Greenberger–Horne–Zeilinger state for neutral atoms

“…As a representative multipartite entanglement, Greenberger–Horne–Zeilinger (GHZ) states reflect unique nonlocal correlations which are important for understanding the fundamental principles of quantum entanglement 52‐54 . Besides, they supply efficient manners for large‐scale cluster state generation, 55,56 quantum metrology, 57‐59 and high‐precision spectroscopy 60,61 .…”