Tag Archives: manufacturing

Illustration of superconducting detectors on arrayed waveguides on a photonic integrated circuit for detection of single photons.

Credit: F. Najafi/ MIT

Toward quantum chips

Packing single-photon detectors on an optical chip is a crucial step toward quantum-computational circuits.

By Larry Hardesty


CAMBRIDGE, Mass. – A team of researchers has built an array of light detectors sensitive enough to register the arrival of individual light particles, or photons, and mounted them on a silicon optical chip. Such arrays are crucial components of devices that use photons to perform quantum computations.

Single-photon detectors are notoriously temperamental: Of 100 deposited on a chip using standard manufacturing techniques, only a handful will generally work. In a paper appearing today in Nature Communications, the researchers at MIT and elsewhere describe a procedure for fabricating and testing the detectors separately and then transferring those that work to an optical chip built using standard manufacturing processes.

Illustration of superconducting detectors on arrayed waveguides on a photonic integrated circuit for detection of single photons. Credit: F. Najafi/ MIT
Illustration of superconducting detectors on arrayed waveguides on a photonic integrated circuit for detection of single photons.
Credit: F. Najafi/ MIT

In addition to yielding much denser and larger arrays, the approach also increases the detectors’ sensitivity. In experiments, the researchers found that their detectors were up to 100 times more likely to accurately register the arrival of a single photon than those found in earlier arrays.

“You make both parts — the detectors and the photonic chip — through their best fabrication process, which is dedicated, and then bring them together,” explains Faraz Najafi, a graduate student in electrical engineering and computer science at MIT and first author on the new paper.

Thinking small

According to quantum mechanics, tiny physical particles are, counterintuitively, able to inhabit mutually exclusive states at the same time. A computational element made from such a particle — known as a quantum bit, or qubit — could thus represent zero and one simultaneously. If multiple qubits are “entangled,” meaning that their quantum states depend on each other, then a single quantum computation is, in some sense, like performing many computations in parallel.

With most particles, entanglement is difficult to maintain, but it’s relatively easy with photons. For that reason, optical systems are a promising approach to quantum computation. But any quantum computer — say, one whose qubits are laser-trapped ions or nitrogen atoms embedded in diamond — would still benefit from using entangled photons to move quantum information around.

“Because ultimately one will want to make such optical processors with maybe tens or hundreds of photonic qubits, it becomes unwieldy to do this using traditional optical components,” says Dirk Englund, the Jamieson Career Development Assistant Professor in Electrical Engineering and Computer Science at MIT and corresponding author on the new paper. “It’s not only unwieldy but probably impossible, because if you tried to build it on a large optical table, simply the random motion of the table would cause noise on these optical states. So there’s been an effort to miniaturize these optical circuits onto photonic integrated circuits.”

The project was a collaboration between Englund’s group and the Quantum Nanostructures and Nanofabrication Group, which is led by Karl Berggren, an associate professor of electrical engineering and computer science, and of which Najafi is a member. The MIT researchers were also joined by colleagues at IBM and NASA’s Jet Propulsion Laboratory.

Relocation

The researchers’ process begins with a silicon optical chip made using conventional manufacturing techniques. On a separate silicon chip, they grow a thin, flexible film of silicon nitride, upon which they deposit the superconductor niobium nitride in a pattern useful for photon detection. At both ends of the resulting detector, they deposit gold electrodes.

Then, to one end of the silicon nitride film, they attach a small droplet of polydimethylsiloxane, a type of silicone. They then press a tungsten probe, typically used to measure voltages in experimental chips, against the silicone.

“It’s almost like Silly Putty,” Englund says. “You put it down, it spreads out and makes high surface-contact area, and when you pick it up quickly, it will maintain that large surface area. And then it relaxes back so that it comes back to one point. It’s like if you try to pick up a coin with your finger. You press on it and pick it up quickly, and shortly after, it will fall off.”

With the tungsten probe, the researchers peel the film off its substrate and attach it to the optical chip.

In previous arrays, the detectors registered only 0.2 percent of the single photons directed at them. Even on-chip detectors deposited individually have historically topped out at about 2 percent. But the detectors on the researchers’ new chip got as high as 20 percent. That’s still a long way from the 90 percent or more required for a practical quantum circuit, but it’s a big step in the right direction.

Source: MIT News Office

Engineers just completed hot-fire testing with two 3-D printed rocket injectors. Certain features of the rocket components were designed to increase rocket engine performance. The injector mixed liquid oxygen and gaseous hydrogen together, which combusted at temperatures over 6,000 degrees Fahrenheit, producing more than 20,000 pounds of thrust.
Image Credit: NASA photo/David Olive

Sparks Fly as NASA Pushes the Limits of 3-D Printing Technology

NASA has successfully tested the most complex rocket engine parts ever designed by the agency and printed with additive manufacturing, or 3-D printing, on a test stand at NASA’s Marshall Space Flight Center in Huntsville, Alabama.

Engineers just completed hot-fire testing with two 3-D printed rocket injectors. Certain features of the rocket components were designed to increase rocket engine performance. The injector mixed liquid oxygen and gaseous hydrogen together, which combusted at temperatures over 6,000 degrees Fahrenheit, producing more than 20,000 pounds of thrust. Image Credit: NASA photo/David Olive
Engineers just completed hot-fire testing with two 3-D printed rocket injectors. Certain features of the rocket components were designed to increase rocket engine performance. The injector mixed liquid oxygen and gaseous hydrogen together, which combusted at temperatures over 6,000 degrees Fahrenheit, producing more than 20,000 pounds of thrust.
Image Credit: NASA photo/David Olive

NASA engineers pushed the limits of technology by designing a rocket engine injector –a highly complex part that sends propellant into the engine — with design features that took advantage of 3-D printing. To make the parts, the design was entered into the 3-D printer’s computer. The printer then built each part by layering metal powder and fusing it together with a laser, a process known as selective laser melting.

The additive manufacturing process allowed rocket designers to create an injector with 40 individual spray elements, all printed as a single component rather than manufactured individually. The part was similar in size to injectors that power small rocket engines and similar in design to injectors for large engines, such as the RS-25 engine that will power NASA’s Space Launch System (SLS) rocket, the heavy-lift, exploration class rocket under development to take humans beyond Earth orbit and to Mars.

“We wanted to go a step beyond just testing an injector and demonstrate how 3-D printing could revolutionize rocket designs for increased system performance,” said Chris Singer, director of Marshall’s Engineering Directorate. “The parts performed exceptionally well during the tests.”

Using traditional manufacturing methods, 163 individual parts would be made and then assembled. But with 3-D printing technology, only two parts were required, saving time and money and allowing engineers to build parts that enhance rocket engine performance and are less prone to failure.

Two rocket injectors were tested for five seconds each, producing 20,000 pounds of thrust. Designers created complex geometric flow patterns that allowed oxygen and hydrogen to swirl together before combusting at 1,400 pounds per square inch and temperatures up to 6,000 degrees Fahrenheit. NASA engineers used this opportunity to work with two separate companies — Solid Concepts in Valencia, California, and Directed Manufacturing in Austin, Texas. Each company printed one injector.

“One of our goals is to collaborate with a variety of companies and establish standards for this new manufacturing process,” explained Marshall propulsion engineer Jason Turpin. “We are working with industry to learn how to take advantage of additive manufacturing in every stage of space hardware construction from design to operations in space. We are applying everything we learn about making rocket engine components to the Space Launch System and other space hardware.”

Additive manufacturing not only helped engineers build and test a rocket injector with a unique design, but it also enabled them to test faster and smarter. Using Marshall’s in-house capability to design and produce small 3-D printed parts quickly, the propulsion and materials laboratories can work together to apply quick modifications to the test stand or the rocket component.

 

https://www.youtube.com/embed/nyveRd36FR8?enablejsapi=1&rel=0

[Video:

3-D Printed Rocket Injector Roars to Life: The most complex 3-D printed rocket injector ever built by NASA roars to life on the test stand at NASA’s Marshall Space Flight Center in Huntsville, Alabama]

“Having an in-house additive manufacturing capability allows us to look at test data, modify parts or the test stand based on the data, implement changes quickly and get back to testing,” said Nicholas Case, a propulsion engineer leading the testing. “This speeds up the whole design, development and testing process and allows us to try innovative designs with less risk and cost to projects.”

Marshall engineers have tested increasingly complex injectors, rocket nozzles and other components with the goal of reducing the manufacturing complexity and the time and cost of building and assembling future engines. Additive manufacturing is a key technology for enhancing rocket designs and enabling missions into deep space.