April 2, 2023

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

Due to the fact that the atom and the photon are entangled, controling the atom also impacts the state of the photon. Furthermore, because photons can simultaneously exist in two states at as soon as, a specific photon can flow in both directions at when, which represents a value that is a combination of 0 and 1 at the same time.
The photon then communicates with the atom, causing the two to become “knotted,” a quantum phenomenon whereby 2 particles can influence one another even across terrific ranges. Since the atom and the photon are knotted, controling the atom likewise influences the state of its paired photon.
Because you can control the method the atom and photons connect, the same gadget can run lots of different quantum programs.

” Normally, if you wanted to develop this kind of quantum computer, you d need to take potentially thousands of quantum emitters, make them all perfectly equivalent, and after that integrate them into a huge photonic circuit,” stated Ben Bartlett, a PhD prospect in applied physics and lead author of the paper. “Whereas with this style, we just need a handful of fairly simple parts, and the size of the device does not increase with the size of the quantum program you desire to run.”
This remarkably basic design needs just a couple of tools: a fiber optic cable television, a beam splitter, a set of optical switches, and an optical cavity.
An animation of the photonic quantum computer proposed by the researchers. Left wing is the storage ring, which holds numerous counter-propagating photons. On the right is the spreading unit, which is used to manipulate the photonic qubits. The spheres at the top, called “Bloch spheres,” illustrate the mathematical state of the atom and one of the photons. Because the photon and the atom are entangled, manipulating the atom likewise impacts the state of the photon. Credit: Ben Bartlett
Luckily, these parts currently exist and are even commercially available. Theyre also constantly being improved because theyre presently utilized in applications aside from quantum computing. For instance, telecom companies have actually been working to enhance fiber optic cable televisions and optical switches for many years.
” What we are proposing here is building on the effort and the financial investment that people have actually put in for enhancing these components,” said Shanhui Fan, the Joseph and Hon Mai Goodman Professor of the School of Engineering and senior author on the paper. “They are not new components particularly for quantum computation.”
A novel style
The researchers style consists of 2 primary sections: a storage ring and a spreading unit. The storage ring, which functions likewise to memory in a routine computer, is a fiber optic loop holding several photons that take a trip around the ring. Comparable to bits that save information in a classical computer, in this system, each photon represents a quantum bit, or “qubit.” The photons instructions of travel around the storage ring determines the worth of the qubit, which like a bit, can be 0 or 1. Additionally, due to the fact that photons can concurrently exist in two states at the same time, a private photon can flow in both instructions at the same time, which represents a worth that is a mix of 0 and 1 at the exact same time.
Stanford graduate student Ben Bartlett and Shanhui Fan, professor of electrical engineering, have proposed a simpler style for photonic quantum computers utilizing easily offered components. Credit: Courtesy Ben Bartlett/ Rod Searcey
The researchers can manipulate a photon by directing it from the storage ring into the scattering system, where it travels to a cavity consisting of a single atom. The photon then interacts with the atom, causing the two to become “knotted,” a quantum phenomenon where 2 particles can affect one another even across great distances. The photon returns to the storage ring, and a laser alters the state of the atom. Controling the atom also affects the state of its paired photon because the photon and the atom are entangled.
” By determining the state of the atom, you can teleport operations onto the photons,” Bartlett stated. “So we just need the one manageable atomic qubit and we can use it as a proxy to indirectly control all of the other photonic qubits.”
Since any quantum logic gate can be compiled into a sequence of operations performed on the atom, you can, in concept, run any quantum program of any size using only one manageable atomic qubit. To run a program, the code is translated into a series of operations that direct the photons into the scattering unit and control the atomic qubit. The very same gadget can run many different quantum programs since you can control the way the atom and photons connect.
” For lots of photonic quantum computers, the gates are physical structures that photons go through, so if you wish to change the program thats running, it frequently includes physically reconfiguring the hardware,” Bartlett said. “Whereas in this case, you do not need to alter the hardware– you simply require to give the device a different set of instructions.”
Reference: “Deterministic photonic quantum computation in an artificial time measurement” by Ben Bartlett, Avik Dutt and Shanhui Fan, 29 November 2021, Optica.DOI: 10.1364/ OPTICA.424258.
Stanford postdoctoral scholar Avik Dutt is also 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 Energy.
This research was funded by the U.S. Department of Defense and the U.S. Air Force Office of Scientific Research.

A fairly easy quantum computer style that utilizes a single atom to manipulate photons might be built with presently readily available elements.
Now, Stanford University researchers have proposed a simpler design for photonic quantum computer systems using readily available parts, according to a paper published on November 29, 2021, in Optica. Their proposed style uses a laser to control a single atom that, in turn, can modify the state of the photons via a phenomenon called “quantum teleportation.” The atom can be reset and recycled for numerous quantum gates, removing the requirement to construct multiple distinct physical gates, significantly lowering the intricacy of constructing a quantum computer system.