Entanglement in a Quantum Annealing Processor

Figure 5A new paper published today in Phys Rev X. It demonstrates eight qubit entanglement in a D-Wave processor, which I believe is a world record for solid state qubits. This is an exceptional paper with an important result. The picture to the left measures a quantity that, if negative, verifies entanglement. The quantity s is the time — the quantum annealing procedure goes from the left to the right, with entanglement maximized near the area where the energy gap is smallest.

Here is the abstract:

Entanglement lies at the core of quantum algorithms designed to solve problems that are intractable by classical approaches. One such algorithm, quantum annealing (QA), provides a promising path to a practical quantum processor. We have built a series of architecturally scalable QA processors consisting of networks of manufactured interacting spins (qubits). Here, we use qubit tunneling spectroscopy to measure the energy eigenspectrum of two- and eight-qubit systems within one such processor, demonstrating quantum coherence in these systems. We present experimental evidence that, during a critical portion of QA, the qubits become entangled and entanglement persists even as these systems reach equilibrium with a thermal environment. Our results provide an encouraging sign that QA is a viable technology for large scale quantum computing.

5 thoughts on “Entanglement in a Quantum Annealing Processor

    • Hi Diana! Well the result is fairly old — we’ve known about this internally for about three years now, and we’ve been able to do this on much larger systems and obtained similar results. So we know there is substantial entanglement in these types of systems. Right now we’re trying to characterize how to use it to gain what Google calls ‘quantum supremacy’. Very good progress on that…

  1. Pingback: A Bet Lost, Despite Entanglement | Wavewatching

  2. Since you guys are able to entangle particles, would you, in theory, be able to set up two access points on different continents both powered by quantum computers in order to have instantaneous communication between two different parts of the globe?

    • No. For several reasons. Here are two:

      1. Entanglement doesn’t imply (useful) instantaneous communication. Communication is bounded by the speed of light. Faster that light communication breaks causality.

      2. The entanglement generated in our technology is between qubits on a processor that’s about 2 inches square. It might be possible to do some type of Bell inequality measurement on the chip itself. If someone else wants to do that, that would be cool. But personally I don’t see the point.

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