Artificial Atoms Unlock Quantum Computing Breakthrough

Hybrid Integration of Designer Nanodiamond With Photonic Circuits via Ring Resonators

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Hybrid integration of a designer nanodiamond with photonic circuits through ring resonators. Credit
Steven Burrows/Sun Group

JILA breakthrough in integrating synthetic atoms with photonic circuits advances quantum computing effectivity and scalability.

In quantum data science, many particles can act as “bits,” from particular person atoms to photons. At JILA, researchers make the most of these bits as “qubits,” storing and processing quantum 1s or 0s by a singular system.

While many JILA Fellows give attention to qubits present in nature, reminiscent of atoms and ions, JILA Associate Fellow and University of Colorado Boulder Assistant Professor of Physics Shuo Sun is taking a special method by utilizing “artificial atoms,” or semiconducting nanocrystals with distinctive digital properties. By exploiting the atomic dynamics inside fabricated diamond crystals, physicists like Sun can produce a brand new kind of qubit, often known as a “solid-state qubit,” or a man-made atom.

Photonic Circuits and Integration Challenges

Because these synthetic atoms don’t transfer, one approach to allow them to discuss to one another is to position them inside a photonic circuit. The photons touring contained in the photonic circuit can join totally different synthetic atoms. Like scorching air shifting by an air duct to heat a chilly room, photons transfer by the quantum circuit to induce interactions between the factitious atoms. “Having an interface between artificial atoms and photons allows you to achieve precise control of the interactions between two artificial atoms,” defined Sun.

Historically, there have been issues with integrating synthetic atoms with photonic circuits. This is as a result of creating the factitious atoms (the place atoms are knocked out of a diamond crystal) is a really random course of, resulting in random placement of the factitious atoms, random variety of synthetic atoms at every location, and random coloration every synthetic atom emits.

Adding to the difficulty is the incompatibility between the fabric that hosts the factitious atoms and the fabric that hosts the photonic circuit. Despite years of analysis, scientists have but to discover a appropriate materials that may be a superb host of each, making the combination tougher.
In a brand new Nano Letters paper, Sun, his analysis group, and collaborators from Stanford University proposed a brand new methodology that might pave the way in which to fixing these two challenges, enabling a extra sophisticated built-in quantum photonic circuit.

This new method suggests larger implications for the way forward for quantum data science, together with a approach to scale up the circuits. “We now have a way to integrate multiple artificial atoms on one photonic chip,” defined first writer and JILA graduate scholar Kin Fung Ngan.

Combining Diamonds With Other Materials

Historically, diamond has been a well-liked selection for internet hosting synthetic atoms, because it’s extremely pure with a big bandgap, permitting physicists extra management over the excitation of the atom contained in the crystal.

“Our qubits are embedded into the diamond,” defined Ngan. “The benefit here is that we don’t need any additional apparatus to hold them in space.”

However, the draw back of utilizing a diamond as a qubit host is that it’s extremely arduous to carve, making it tough to outline photonic circuits on them. It can be tough to get a big diamond piece, in contrast to different photonic supplies reminiscent of silicon nitride, the place eight-inch wafers are available.

To make a big quantum photonic circuit, the diamond-based synthetic atoms have to be positioned inside a photonic circuit primarily based on a special materials, reminiscent of silicon nitride. Sun, Ngan, and JILA graduate scholar Yuan Zhan needed to discover methods to combine the 2 totally different elements residing in numerous supplies. “If the integration was not achieved properly, you may have a weaker coupling between the atom and the photon or a loss of photons during transmission. These effects will generate errors when we use photons to mediate interactions between two artificial atoms,” elaborated Sun.

While earlier research tried to mix the 2 supplies utilizing exterior junctions, the researchers took a special method by embedding a nanosized chunk of diamond containing the factitious atom immediately contained in the silicon nitride circuit. Using an ultraprecise placement methodology for arranging the nanodiamonds on the chip, the researchers added nanodiamonds containing a man-made atom to the chip, coated your entire chip with a silicon nitride layer, after which fabricated photonic circuits centered round every atom. This course of ensures the utmost coupling between the factitious atom and the photonic circuit.

Testing the New Experimental Setup

After embedding the factitious atoms into the silicon nitride circuit, the researchers examined the coupling effectivity by thrilling the factitious atoms and measuring the sunshine collected by the photonic circuit. Their exams confirmed that the sunshine shone brighter when the atom was positioned inside an optical cavity, revealing the power to effectively couple mild from the factitious atom to the photonic circuit.

Besides contributing to raised compatibility, the ultraprecise placement method allowed researchers to align a number of synthetic atoms in a row on the identical circuit, exhibiting the flexibleness of their course of and its functionality to host a number of qubits without delay. Currently, Ngan, Zhan, and different JILA researchers are engaged on methods to make these synthetic atoms work together with one another with the assistance of photons and to entangle two synthetic atoms with the assistance of photons.

A Duality in Design

While this present quantum photonic circuit leverages photons as mediators for interactions between the factitious atoms (or qubits), the photons themselves may also act as separate qubits throughout the system.

“The circuit can indeed work for two purposes,” Sun elaborated. “By embedding artificial atoms inside a photonic quantum circuit, we can use the artificial atoms as sources and memories of single photons, potentially reducing the resource required to build a photonic quantum processor.”

The mixture of the fabric compatibility and the duality of the qubits within the system means that Sun’s circuit design might have huge implications for the way forward for quantum data, providing an efficient approach to scale up the built-in quantum photonic techniques.

Reference: “Quantum Photonic Circuits Integrated with Color Centers in Designer Nanodiamonds” by Kinfung Ngan, Yuan Zhan, Constantin Dory, Jelena Vučković and Shuo Sun, 2 October 2023, Nano Letters.
DOI: 10.1021/acs.nanolett.3c02645