# Decoherence of up to 8-qubit entangled states in a 16-qubit superconducting quantum processor

@article{Ozaeta2017DecoherenceOU, title={Decoherence of up to 8-qubit entangled states in a 16-qubit superconducting quantum processor}, author={A. Ozaeta and P. McMahon}, journal={arXiv: Quantum Physics}, year={2017} }

We report on the coherence of Greenberger-Horne-Zeilinger (GHZ) states comprised of up to 8 qubits in the IBM ibmqx5 16-qubit quantum processor. In particular, we evaluate the coherence of GHZ states with $N=1,\ldots,8$ qubits, as a function of a delay time between state creation and measurement. We find that the decay in coherence occurs at a rate that is linear in the number of qubits. This is consistent with a model in which the dominant noise affecting the system is uncorrelated across… Expand

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#### References

SHOWING 1-10 OF 17 REFERENCES

Quantum Volume

- 2017

As we build larger quantum computing devices capable of performing more complicated algorithms, it is important to quantify their power. The origin of a quantum computer’s power is already subtle,… Expand

Noisy metrology beyond the standard quantum limit.

- Physics, Medicine
- Physical review letters
- 2013

It is shown that precision can be significantly enhanced when the noise is concentrated along some spatial direction, while the Hamiltonian governing the evolution which depends on the parameter to be estimated can be engineered to point along a different direction. Expand

Going Beyond Bell’s Theorem

- Mathematics, Physics
- 1989

Bell’s Theorem proved that one cannot in general reproduce the results of quantum theory with a classical, deterministic local model. However, Einstein originally considered the case where one could… Expand

Nature 549

- 203
- 2017

Physical Review A 95

- 022121
- 2017

npj Quantum Information 3

- 2
- 2017

Physical Review A 89

- 042334
- 2014

Quantum Info

- Comput. 13, 181
- 2013

Science 339

- 1169
- 2013