Implementing efficient selective quantum process tomography of superconducting quantum gates on IBM quantum experience

Abstract

The experimental implementation of selective quantum process tomography (SQPT) involves computing individual elements of the process matrix with the help of a special set of states called quantum 2-design states. However, the number of experimental settings required to prepare input states from quantum 2-design states to selectively and precisely compute a desired element of the process matrix is still high, and hence constructing the corresponding unitary operations in the lab is a daunting task. In order to reduce the experimental complexity, we mathematically reformulated the standard SQPT problem, which we term the modified SQPT (MSQPT) method. We designed the generalized quantum circuit to prepare the required set of input states and formulated an efficient measurement strategy aimed at minimizing the experimental cost of SQPT. We experimentally demonstrated the MSQPT protocol on the IBM QX2 cloud quantum processor and selectively characterized various two- and three-qubit quantum gates.

Using Cryogenic CMOS Control Electronics To Enable A Two–Qubit Cross–Resonance Gate

“…Alternatively, new measurement techniques with lower memory overhead could be adapted to extract error rates, e.g. : using simple characterization measurements along with error models to infer errors [38][39][40][41], interpreting the error through an under-sampled RB experiment [42], or performing experiments like quantum process tomography [43,44] that place lesser demands on memory. It is also worth noting that longer sequences may not be needed in future quantum computers.…”

Experimental construction of a symmetric three-qubit entangled state and its utility in testing the violation of a Bell inequality on an NMR quantum simulator

“…The duration of pulses U P 1 , U P 2 , U P 3 , U P 4 are 500 μs, 9000 μs, 7500 μs, 4000 μs, respectively. The experimental state was reconstructed using a least squares constrained convex optimization technique [45]. The set of tomographic operations {III, IIY, IY Y, Y II, XY X, XXY, XXX} where the X(Y ) denotes the single spin operator implemented by a spin-selective π 2 pulse and I denotes no operation were performed to reconstruct the final density operator.…”

Parallel tomography of quantum non-demolition measurements in multi-qubit devices

“…Quantum tomography (QT) is a powerful and general technique to characterize the evolution of a physical system 37 , used e.g. in superconducting qubits [38][39][40] , trapped ions [41][42][43] , or photonic systems [44][45][46] . We proposed QND measurement tomography (QND-MT) 47 as a self-consistent reconstruction of the Choi operators for a general QND detector, describing the measurement process, its dynamics, relevant quantifiers, and sources of error.…”