D-Wave Systems opened up free cloud access to its quantum computing resources for researchers responding to COVID-19. They're also enlisting their staff, partners, and customers to help others get up to speed on programming quantum computing for their specific tasks. By taking advantage of quantum weirdness – the ability of quantum bits (qubits) to exist in both a “one” and a “zero” state at the same time – these systems can potentially solve problems that cripple even the fastest of today’s supercomputers. From IEEE Spectrum:

Since 2018, D-Wave has offered remote access to quantum computing via its “Leap” quantum cloud computing service. Baratz says an ecosystem of more than 1,000 developers has sprung up to apply Leap’s quantum computing resources to a variety of purposes, including protein folding and financial modeling, and optimizing public transportation routes in Lisbon, Portugal.

Then, in February, D-Wave began offering an enhanced quantum computing cloud service (Leap 2) which couples simulated qubits (on a conventional computer) with D-Wave’s actual qubits.

“We’ve seen problems being explored in the following areas: 1) the modeling and simulation of the spread of the virus, 2) the scheduling of nurses and other hospital resources, 3) assessing the rate of virus mutation, and 4) the assessment of existing drugs as potential treatments,” Baratz said. “We've heard positive feedback from organizations and developers around the world and are looking forward to their collaboration with our global partners to find potential solutions to COVID-19."

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In normal life, you open the car door before getting into the car. Operation A happens before operation B. That's the causal order of things. But a new quantum switch weirdly enables two operations to happen simultaneously. From Science News:

The device, known as a quantum switch, works by putting particles of light through a series of two operations — labeled A and B — that alter the shape of the light. These photons can travel along two separate paths to A and B. Along one path, A happens before B, and on the other, B happens before A.

Which path the photon takes is determined by its polarization, the direction in which its electromagnetic waves wiggle — up and down or side to side. Photons that have horizontal polarization experience operation A first, and those with vertical polarization experience B first.

But, thanks to the counterintuitive quantum property of superposition, the photon can be both horizontally and vertically polarized at once. In that case, the light experiences both A before B, and B before A, Romero and colleagues report.

While this is deeply weird and amazing, it unfortunately doesn't occur at the human scale but rather in the quantum realm where measurements are in the nanometers. Still, quantum switches do have clear applications in future communications and computation systems.

"Indefinite Causal Order in a Quantum Switch" (Physical Review Letters)

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