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Quantum approximate optimization of non-planar graph problems on a planar superconducting processor
TLDR
The application of the Google Sycamore superconducting qubit quantum processor to combinatorial optimization problems with the quantum approximate optimization algorithm (QAOA) is demonstrated and an approximation ratio is obtained that is independent of problem size and for the first time, that performance increases with circuit depth.
Asymmetric quantum error-correcting codes
The noise in physical qubits is fundamentally asymmetric: in most devices, phase errors are much more probable than bit flips. We propose a quantum error-correcting code that takes advantage of this
Hartree-Fock on a superconducting qubit quantum computer
TLDR
Several quantum simulations of chemistry with up to one dozen qubits are performed, including modeling the isomerization mechanism of diazene, and error-mitigation strategies based on N-representability that dramatically improve the effective fidelity of the experiments are demonstrated.
Localization of preformed Cooper pairs in disordered superconductors
Disorder leads to localization of electrons at low temperatures, changing metals to insulators. In a superconductor the electrons are paired up, and scanning tunnelling microscopy shows that the
Coherent quantum phase slip
TLDR
Direct observation of CQPS in a narrow segment of a superconducting loop made of strongly disordered indium oxide is reported; the effect is made manifest through the superposition of quantum states with different numbers of flux quanta, which should lead to new applications insuperconducting electronics and quantum metrology.
Superconductor-Insulator transition and energy localization
We develop an analytical theory for generic disorder-driven quantum phase transitions. We apply this formalism to the superconductor-insulator transition and we briefly discuss the applications to
Microscopic origin of low-frequency flux noise in josephson circuits.
TLDR
It is argued that this noise is produced by spins at superconductor insulator boundary whose dynamics is due to RKKY interaction, and this mechanism explains size independence of the noise, different frequency dependences of the spectra reported in large and small SQUIDs, and gives the correct intensity for realistic parameters.
Correlated charge noise and relaxation errors in superconducting qubits.
TLDR
A superconducting multiqubit circuit is characterized and it is found that charge noise in the chip is highly correlated on a length scale over 600 micrometres; moreover, discrete charge jumps are accompanied by a strong transient reduction of qubit energy relaxation time across the millimetre-scale chip.
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