Even on the world's most powerful supercomputers, quantum computers can perform certain tasks that are hard to complete. In the future, scientists anticipate using quantum computing to emulate materials systems, simulation of quantum chemistry, and improve hard tasks, with impacts that could span finance to pharmaceuticals.
To realize this promise, you need resilient and extendable hardware. One challenge in building a large-scale quantum computer is that researchers need to find a way to separate smaller-scale processing from larger-scale data. Conventional techniques used to communicate electronic information don't translate to quantum devices because quantum computers are fundamentally different from classical computers. One requirement is certain, whether it's via a classical or a quantum interconnect.
MIT researchers have developed a quantum computing architecture that will allow high fidelity communication between quantum processors. MIT researchers demonstrate the emission of single photons in a user-defined direction. More than 96 percent of the time, quantum information flows in the right direction.
A larger quantum processor network can be created by linking several of these modules.
The co-lead author of a research paper describes quantum interconnects as a crucial step towards modular implementations of larger-scale machines.
Kannan says that the ability to communicate between smaller subsystems will enable a modular architecture for quantum processors, and this may be a simpler way of scaling to larger system sizes compared to using a single large and complicated chip.
Kannan is an electrical engineering and computer science graduate student at the Research Laboratory of Electronics at the Massachusetts Institute of Technology. The associate director of RLE is William D. Oliver, a professor of electrical engineering and computer science.
Quantum information is moving.
In a classical computer, different components perform different functions and electronic information is shuttled between them using wires.
There is more to quantum information than meets the eye. A phenomenon called superposition means that quantum information can be both 0 and 1 at the same time. Particles of light can be used to carry quantum information. It can't be transported using conventional protocols because of the added complexity.
A quantum network uses photons to travel through different types of wires. It is possible to move a photon only to the left or to the right.
The direction in which photon travel is easy to establish is one of the reasons why most architectures use unidirectional waveguides. This approach is difficult to scale due to the fact that more waveguides are needed as the network grows. Communication errors are one of the things that can be introduced by additional components to enforce the directionality.
If we have a way to choose the direction at will, we can get rid of these components. Kannan says that this is the first step towards bidirectional communication.
Multiple modules can be strung along a single wave. The architecture design makes it possible for the same module to be used as both a transmitter and a receiver. Any two modules can send and capture the light.
We only have a single physical connection that can hold a lot of modules. This is the reason it isScalable. We are currently working on capturing the photon downstream at a second module after demonstrating the photon emission from one module.
Enhancing quantum properties.
The module was made of four qubits.
Qubits are the building blocks of quantum computers. It is possible to use qubits as photon emitters. When energy is added to a qubit, it causes it to become excited and emit a photon.
Simply connecting one qubit to another does not guarantee directionality. A single qubit emits a photon, but it can travel to the left or right. The researchers use two qubits and a property called quantum interference to make sure the emitted photon travels in the correct direction.
In a Bell state, the two qubits are in an entangled state. The left qubit is excited and the right qubit is excited. One aspect is excited at a given time, but the other is not.
When the qubits are in this entangled Bell state, the photon is effectively emitted to the waveguide at the two qubit locations simultaneously. The photon emission must travel to either the left or right depending on the relative phase within the Bell state. The researchers choose the direction in which the photon travels when they prepare the Bell state.
The same technique can be used to get the photon at another module.
A module can be prepared to receive the photon by tuning it to the same frequencies. The photon will pass by if they aren't at the same frequencies. It is similar to tuning a radio. The music will be picked up if we choose the right radio frequencies.
If they wanted to emit a photon to the right, 96 percent of the time it went to the right, they used their technique.
The researchers want to connect multiple modules and use the process to emit and absorb photons after using this technique. A modular architecture that combines many smaller-scale processors into one larger-scale and more powerful quantum processor is in the works.
There is more information about Bharath Kannan and Nature Physics. The article can be found at www.nature.com/articles/s4156
Journal information: Nature Physics
All Rights Reserved © 2024
