Probing Quantum Telecloning on Superconducting Quantum Processors
Quantum information can not be perfectly cloned, but approximate copies of
quantum information can be generated. Quantum telecloning combines approximate
quantum cloning, more typically referred as quantum cloning, and quantum
teleportation. Quantum telecloning allows approximate copies of quantum
information to be constructed by separate parties, using the classical results
of a Bell measurement made on a prepared quantum telecloning state. Quantum
telecloning can be implemented as a circuit on quantum computers using a
classical co-processor to compute classical feed forward instructions using if
statements based on the results of a mid-circuit Bell measurement in real time.
We present universal, symmetric, optimal $1 \rightarrow M$ telecloning
circuits, and experimentally demonstrate these quantum telecloning circuits for
$M=2$ up to $M=10$, natively executed with real time classical control systems
on IBM Quantum superconducting processors, known as dynamic circuits. We
perform the cloning procedure on many different message states across the Bloch
sphere, on $7$ IBM Quantum processors, optionally using the error suppression
technique X-X sequence digital dynamical decoupling. Two circuit optimizations
are utilized, one which removes ancilla qubits for $M=2, 3$, and one which
reduces the total number of gates in the circuit but still uses ancilla qubits.
Parallel single qubit tomography with MLE density matrix reconstruction is used
in order to compute the mixed state density matrices of the clone qubits, and
clone quality is measured using quantum fidelity. These results present one of
the largest and most comprehensive NISQ computer experimental analyses on
(single qubit) quantum telecloning to date. The clone fidelity sharply
decreases to $0.5$ for $M > 5$, but for $M=2$ we are able to achieve a mean
clone fidelity of up to $0.79$ using dynamical decoupling.
Elijah Pelofske Andreas Bärtschi Stephan Eidenbenz Bryan Garcia Boris Kiefer