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Stanford’s Simple New Quantum Computer Design: Photonic Computation in a Synthetic Time Dimension

Optical Computer Concept

A comparatively easy quantum laptop design that makes use of a single atom to control photons could possibly be constructed with at the moment obtainable parts.

Now, Stanford College researchers have proposed a easier design for photonic quantum computer systems utilizing available parts, in response to a paper printed on November 29, 2021, in Optica. Their proposed design makes use of a laser to control a single atom that, in flip, can modify the state of the photons through a phenomenon referred to as “quantum teleportation.” The atom will be reset and reused for a lot of quantum gates, eliminating the necessity to construct a number of distinct bodily gates, vastly lowering the complexity of constructing a quantum laptop.

“Usually, for those who wished to construct such a quantum laptop, you’d need to take doubtlessly 1000’s of quantum emitters, make all of them completely indistinguishable, after which combine them into a big photonic circuit,” mentioned Ben Bartlett, a PhD candidate in utilized physics and lead creator of the paper. “Whereas with this design, we solely want a handful of comparatively easy parts, and the dimensions of the machine doesn’t enhance with the dimensions of the quantum program you need to run.”

This remarkably easy design requires solely a few items of kit: a fiber optic cable, a beam splitter, a pair of optical switches, and an optical cavity.

An animation of the photonic quantum laptop proposed by the researchers. On the left is the storage ring, which holds a number of counter-propagating photons. On the precise is the scattering unit, which is used to control the photonic qubits. The spheres on the prime, referred to as “Bloch spheres,” depict the mathematical state of the atom and one of many photons. As a result of the atom and the photon are entangled, manipulating the atom additionally impacts the state of the photon. Credit score: Ben Bartlett

Happily, these parts exist already and are even commercially obtainable. They’re additionally frequently being refined since they’re at the moment used in functions aside from quantum computing. For instance, telecommunications corporations have been working to enhance fiber optic cables and optical switches for years.

“What we’re proposing right here is constructing upon the trouble and the funding that folks have put in for enhancing these parts,” mentioned Shanhui Fan, the Joseph and Hon Mai Goodman Professor of the College of Engineering and senior creator on the paper. “They aren’t new parts particularly for quantum computation.”

The scientists’ design consists of two major sections: a storage ring and a scattering unit. The storage ring, which capabilities equally to reminiscence in a common laptop, is a fiber optic loop holding a number of photons that journey across the ring. Analogous to bits that retailer info in a classical laptop, in this method, every photon represents a quantum bit, or “qubit.” The photon’s path of journey across the storage ring determines the worth of the qubit, which like a bit, will be 0 or 1. Moreover, as a result of photons can concurrently exist in two states without delay, a person photon can move in each instructions without delay, which represents a worth that’s a mixture of 0 and 1 on the similar time.

Stanford graduate pupil Ben Bartlett and Shanhui Fan, professor {of electrical} engineering, have proposed a easier design for photonic quantum computer systems utilizing available parts. Credit score: Courtesy Ben Bartlett / Rod Searcey

The researchers can manipulate a photon by directing it from the storage ring into the scattering unit, the place it travels to a cavity containing a single atom. The photon then interacts with the atom, inflicting the 2 to turn out to be “entangled,” a quantum phenomenon whereby two particles can affect each other even throughout nice distances. Then, the photon returns to the storage ring, and a laser alters the state of the atom. As a result of the atom and the photon are entangled, manipulating the atom additionally influences the state of its paired photon.

“By measuring the state of the atom, you may teleport operations onto the photons,” Bartlett mentioned. “So we solely want the one controllable atomic qubit and we will use it as a proxy to not directly manipulate the entire different photonic qubits.”

As a result of any quantum logic gate will be compiled into a sequence of operations carried out on the atom, you may, in precept, run any quantum program of any measurement utilizing just one controllable atomic qubit. To run a program, the code is translated into a sequence of operations that direct the photons into the scattering unit and manipulate the atomic qubit. As a result of you may management the way in which the atom and photons work together, the identical system can run many alternative quantum applications.

“For a lot of photonic quantum computer systems, the gates are bodily constructions that photons cross by means of, so if you wish to change this system that’s working, it typically includes bodily reconfiguring the {hardware},” Bartlett mentioned. “Whereas in this case, you don’t want to vary the {hardware} – you simply want to present the machine a completely different set of directions.”

Reference: “Deterministic photonic quantum computation in a artificial time dimension” by Ben Bartlett, Avik Dutt and Shanhui Fan, 29 November 2021, Optica.
DOI: 10.1364/OPTICA.424258

Stanford postdoctoral scholar Avik Dutt can also be co-author of this paper. Fan is a professor {of electrical} engineering, a member of Stanford Bio-X and an affiliate of the Precourt Institute for Power.

This analysis was funded by the U.S. Division of Protection and the U.S. Air Drive Workplace of Scientific Analysis.

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