November 29, 2017 feature

# Physicists set new record with 10-qubit entanglement

Lead researcher Jian-Wei Pan and co-workers at the University of Science and Technology of China, Zhejiang University, Fuzhou University, and the Institute of Physics, China, have published a paper on their results in a recent issue of *Physical Review Letters*.

In general, one of the biggest challenges to scaling up multiqubit entanglement is addressing the catastrophic effects of decoherence. One strategy is to use superconducting circuits, which operate at very cold temperatures and consequently have longer qubit coherence times.

In the new set-up, the researchers used qubits made of tiny pieces of aluminum, which they connected to each other and arranged in a circle around a central bus resonator. The bus is a key component of the system, as it controls the interactions between qubits, and these interactions generate the entanglement.

As the researchers demonstrated, the bus can create entanglement between any two qubits, can produce multiple entangled pairs, or can entangle up to all 10 qubits. Unlike some previous demonstrations, the entanglement does not require a series of quantum logic gates, nor does it involve modifying the physical wiring of the circuit, but instead all 10 qubits can be entangled with a single collective qubit-bus interaction.

To measure how well the qubits are entangled, the researchers used quantum tomography to determine the probability of measuring every possible state of the system. Although there are thousands of such states, the resulting probability distribution yielded the correct state about 67% of the time. This fidelity is well above the threshold for genuine multipartite entanglement (generally considered to be about 50%).

In the future, the physicists' goal is to develop a quantum simulator that could simulate the behavior of small molecules and other quantum systems, which would allow for a more efficient analysis of these systems compared to what is possible with classical computers.

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**More information:**Chao Song et al. "10-Qubit Entanglement and Parallel Logic Operations with a Superconducting Circuit."

*Physical Review Letters*. DOI: 10.1103/PhysRevLett.119.180511

Also at arXiv:1703.10302 [quant-ph]

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**Citation**: Physicists set new record with 10-qubit entanglement (2017, November 29) retrieved 20 June 2019 from https://phys.org/news/2017-11-physicists-qubit-entanglement.html

Two.

Probably the most known quantum computer algorithm is Shor's algorithm for factorization. With a 10 qubit algorithm you can find the prime factors of a number as high as 9 (or 10..it's pretty close).

Conditions are m + n = q

Where

q: is the number of qubits

m = ld N

n = 2*ld N

where ld is the logarithm dualis (log to base two) and N is the number you can find the prime factors of.

Now this might not sound very overwhelming, but consider that this scales pretty quickly (due to the log-dependency)

With 100 qubits you can find the prime factors of something as large as about 10 billion.

With 1000 qubits you can already find the prime factors of a number with 100 digits (which is in the ballpark of current cryptographic problems)