Violation of no-signaling on a public quantum computer
No-signaling is a consequence of the no-communication theorem that states
that bipartite systems cannot transfer information
  unless a communication channel exists. It is also a by-product of the
assumptions of Bell theorem about quantum nonlocality. We have tested
no-signaling in bipartite systems of qubits from IBM Quantum devices in
extremely large statistics, resulting in significant violations. Although the
time and space scales of IBM Quantum cannot in principle rule out subluminal
communications, there is no obvious physical mechanism leading to signaling.
The violation is also at similar level as observed in Bell tests. It is
therefore mandatory to check possible technical imperfections that may cause
the violation and to repeat the loophole-free Bell test at much larger
statistics, in order to be ruled out definitively at strict spacelike
conditions.
Tomasz Rybotycki Tomasz Białecki Josep Batle Adam Bednorz