Can multi-particle systems be too entangled to be useful for quantum computation?

Klaus Mølmer, Anders Søndberg Sørensen

Klaus Mølmer, Anders S⊘rensen

Candidates for quantum computing which offer only restricted control, e.g. due to lack of access to individual qubits, are not useful for general purpose quantum computing. We present concrete proposals for the use of systems with such limitations as RISQ-reduced instruction set quantum computers and devices-for simulation of quantum dynamics, for multi-particle entanglement and squeezing of collective spin variables. These tasks are useful in their own right, and they also provide experimental probes for the functioning of quantum gates in premature prototypes of quantum computers.

Klaus Mølmer, Anders Sørensen

Candidates for quantum computing which offer only restricted control, e.g., due to lack of access to individual qubits, are not useful for general purpose quantum computing.We present concrete proposals for the use of systems with such limitations as RISQreduced instruction set quantum computers and devices -for simulation of quantum dynamics, for multi-particle entanglement and squeezing of collective spin variables.These tasks are useful in their own right, and they also provide experimental probes for the functioning of quantum gates in pre-mature proto-types of quantum computers.

Benoît Vermersch

Bei Zeng, D. L. Zhou, P. Zhang +2 more

We revisit the criterion of multi-particle entanglement based on the overlaps of a given quantum state $ρ$ with maximally entangled states. For a system of $m$ particles, each with $N$ distinct states, we prove that $ρ$ is $m$-particle negative partial transpose (NPT) entangled, if there exists a maximally entangled state $|{\rm MES}>$, such that $>{1}/{N}$. While this sufficiency condition is weaker than the Peres-Horodecki criterion in all cases, it applies to multi-particle systems, and becomes especially useful when the number of particles ($m$) is large. We also consider the converse of this criterion and illustrate its invalidity with counter examples.

H. J. Briegel, S. J. van Enk, J. I. Cirac +9 more