Amazon adds Xanadu’s quantum computer to Bracket service

Amazon adds Xanadu’s quantum computer to Bracket service

Business news |
By Nick Flaherty

Amazon has added a photonic quantum computer from one of the leading developers, Xanadu, to its public Braket cloud service.

“With this launch, we expand the range of quantum technologies customers can access on Amazon Braket to now include a photonic quantum device, in addition to the existing superconducting and ion-trap devices,” said Cedric Lin, Eric Kessler, Jordan Sullivan, and Stefan Natu at Amazon.

Xanadu recently announced the launch of Borealis, its newest quantum computer with 216 squeezed-state qubits. This is almost twenty times more than the previous and is currently the largest photonic quantum computer ever built, and the first of its kind to ever be made accessible to the public.

The Canadian company has raised $135m to build the photonic quantum computer systems.

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Borealis is optimised for a very specific type of mathematical problem known as Gaussian Boson Sampling. Abstractly, this problem refers to generating random numbers that obey certain patterns expressed through a mathematical function called the Hafnian.

This is extremely hard, if not impossible, to compute on a classical computer once the size of the inputs grows beyond a certain point. Borealis was designed to access this space of mathematical problems, allowing remote users to run their own quantum programs to encode matrices, and returning to them the output of the machine — samples from the Hafnian-based probability distribution specified by the user.

Borealis is also the first photonic quantum computer with quantum computational advantage to offer users full programmability over all its gates — over 1200 parameters can be freely specified by the user encoding their program, as well as the brightness of the input squeezed-state qubits.

The computer uses time multiplexing to generate and entangle the quantum states, with a source of squeezed-state qubits producing a train of 216 pulses of squeezed light at 6MHz. Each pulse of squeezed light is made of a quantum superposition of photon pairs, generated by passing bright laser pulses through a special nonlinear crystal inside an optical resonator.

Each pulse, also referred to as a qumode, is squeezed, i.e., prepared in a quantum mechanical state that exhibits distinct characteristics in the photon number distribution. The qumodes, only distinguishable by their respective time signature, are then injected into a sequence of dynamically programmable, loop-based interferometers. These interferometers are at the heart of the GBS experiment, enabling entangling gates between the qumodes: Programmable beam splitters and phase shifters can be set to selectively route qumodes into optical delay lines so they interfere with subsequent pulses, a strategy called temporal multiplexing.

Ih the final step, the state of the system is measured using an array of photon-number resolving detectors based on superconducting transition edge sensors. This non-linear operation projects the state onto a photon number state, or Fock state, which cannot be described anymore as a Gaussian state, and the classical description breaks down. Due to the entanglement in the system, the probabilities of the outcomes from each of the 216 squeezed-state qumodes are not independent, and computing them quickly becomes intractable on a classical computer.

The required classical simulation time on the Fugaku supercomputer in Japan, using state-of-the-art algorithms, would take 9000 years for a single sample of Gaussian Boson Sampling. Borealis produces a result in 36ms.  

Amazon acknowledges that remains to be seen if researchers can devise other, more efficient algorithms, but the computational gap between the classical and quantum computations puts Borealis well into the quantum advantage regime.

Having Borealis on the Bracket service (in the US East region) allows researchers to analyze and study quantum advantage experiments using Strawberry Fields, Xanadu’s open source library for photonic quantum computing.

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