Table 2 Comparison of quantum composition (α) and temporal steerable weight (τ).

From: Quantifying Quantum-Mechanical Processes

Approaches

Target channels

I

H

T

α

0.884

0.836

0.799

τ 8

0.769

0.688

0.603

τ 7

0.768

0.687

0.602

τ 6

0.767

0.677

0.602

τ 5

0.766

0.677

0.600

τ 4

0.765

0.674

0.599

τ 3

0.764

0.671

0.597

τ 2

0.688

0.522

0.391

  1. We consider how temporal steering is demonstrated by single qubits undergoing practical channels in IBM Q35 and quantified in terms of α and τ 57. These experimental channels are created with respect to the gates I, H and T. Here, the subscript of τ n indicates that an assemblage \(\{{\sigma }_{{v}_{k}}^{T}\}\) with n elements has been used to determine τ for the experimental states. In determining τ 2, the eigenstates of X and Y were chosen as the input states of the experimental channels. For n > 2, the eigenstates of X, Y and Z together with 2n − 6 randomly-chosen pure states as the input states were used in calculating τ n . Since our framework is optimal, α is higher than τ n for each experimental channel, irrespective of the type and number of input states chosen to obtain τ.
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