“Having a user interface between artificial atoms and photons enables you to achieve accurate control of the interactions in between 2 synthetic atoms,” described Sun.Historically, there have actually been problems with incorporating synthetic atoms with photonic circuits. This is since creating the synthetic atoms (where atoms are knocked out of a diamond crystal) is a very random process, leading to random placement of the synthetic atoms, random number of artificial atoms at each location, and random color each synthetic atom emits.Adding to the issue is the incompatibility in between the material that hosts the synthetic atoms and the material that hosts the photonic circuit. “We now have a way to integrate several synthetic atoms on one photonic chip,” discussed very first author and JILA graduate student Kin Fung Ngan.Combining Diamonds With Other MaterialsHistorically, diamond has been a popular choice for hosting artificial atoms, as its exceptionally pure with a large bandgap, allowing physicists more control over the excitation of the atom inside the crystal. Currently, Ngan, Zhan, and other JILA scientists are working on methods to make these artificial atoms connect with each other with the aid of photons and to entangle two artificial atoms with the help of photons.A Duality in DesignWhile this existing quantum photonic circuit leverages photons as mediators for interactions in between the synthetic atoms (or qubits), the photons themselves can also act as different qubits within the system.
Hybrid combination of a designer nanodiamond with photonic circuits via ring resonators. CreditSteven Burrows/Sun GroupJILA breakthrough in incorporating synthetic atoms with photonic circuits advances quantum computing effectiveness and scalability.In quantum info science, many particles can act as “bits,” from private atoms to photons. At JILA, researchers use these bits as “qubits,” keeping and processing quantum 1sts or 0s through a distinct system.While many JILA Fellows concentrate on qubits found in nature, such as atoms and ions, JILA Associate Fellow and University of Colorado Boulder Assistant Professor of Physics Shuo Sun is taking a various technique by utilizing “synthetic atoms,” or semiconducting nanocrystals with unique electronic properties. By exploiting the atomic characteristics inside produced diamond crystals, physicists like Sun can produce a new type of qubit, called a “solid-state qubit,” or an artificial atom.Photonic Circuits and Integration ChallengesBecause these artificial atoms do not move, one way to let them talk with each other is to place them inside a photonic circuit. The photons traveling inside the photonic circuit can connect different synthetic atoms. Like hot air moving through an air duct to warm a cold space, photons move through the quantum circuit to induce interactions in between the artificial atoms. “Having an interface between artificial atoms and photons permits you to achieve accurate control of the interactions between two synthetic atoms,” described Sun.Historically, there have been issues with integrating synthetic atoms with photonic circuits. This is since producing the synthetic atoms (where atoms are knocked out of a diamond crystal) is an extremely random procedure, leading to random placement of the synthetic atoms, random variety of artificial atoms at each place, and random color each artificial atom emits.Adding to the concern is the incompatibility in between the product that hosts the artificial atoms and the material that hosts the photonic circuit. Despite years of research, researchers have yet to discover an appropriate product that can be a good host of both, making the integration more difficult.In a new Nano Letters paper, Sun, his research group, and partners from Stanford University proposed a brand-new technique that would pave the method to solving these 2 difficulties, making it possible for a more complicated incorporated quantum photonic circuit.This new strategy recommends bigger implications for the future of quantum information science, including a way to scale up the circuits. “We now have a method to integrate several artificial atoms on one photonic chip,” described very first author and JILA graduate student Kin Fung Ngan.Combining Diamonds With Other MaterialsHistorically, diamond has actually been a popular choice for hosting artificial atoms, as its extremely pure with a large bandgap, enabling physicists more control over the excitation of the atom inside the crystal.” Our qubits are embedded into the diamond,” discussed Ngan. “The benefit here is that we do not require any extra apparatus to hold them in space.” However, the downside of using a diamond as a qubit host is that its extremely hard to carve, making it difficult to specify photonic circuits on them. It is likewise difficult to get a big diamond piece, unlike other photonic materials such as silicon nitride, where eight-inch wafers are easily available.To make a big quantum photonic circuit, the diamond-based artificial atoms must be positioned inside a photonic circuit based upon a different material, such as silicon nitride. Sun, Ngan, and JILA graduate student Yuan Zhan needed to find methods to incorporate the two various elements living in various products. “If the combination was not achieved properly, you might have a weaker coupling in between the atom and the photon or a loss of photons during transmission. These results will produce mistakes when we utilize photons to moderate interactions between 2 synthetic atoms,” elaborated Sun.While previous studies tried to integrate the 2 products using external junctions, the scientists took a various method by embedding a nanosized piece of diamond including the artificial atom directly inside the silicon nitride circuit. Using an ultraprecise placement technique for arranging the nanodiamonds on the chip, the scientists added nanodiamonds containing an artificial atom to the chip, covered the whole chip with a silicon nitride layer, and after that produced photonic circuits centered around each atom. This procedure guarantees the maximum coupling in between the synthetic atom and the photonic circuit.Testing the New Experimental SetupAfter embedding the synthetic atoms into the silicon nitride circuit, the scientists tested the coupling effectiveness by interesting the synthetic atoms and determining the light gathered by the photonic circuit. Their tests showed that the light shone brighter when the atom was placed inside an optical cavity, revealing the capability to efficiently couple light from the artificial atom to the photonic circuit.Besides adding to much better compatibility, the ultraprecise placement technique permitted researchers to line up a number of synthetic atoms in a row on the very same circuit, showing the versatility of their procedure and its ability to host several qubits at the same time. Presently, Ngan, Zhan, and other JILA researchers are dealing with techniques to make these artificial atoms communicate with each other with the assistance of photons and to entangle 2 synthetic atoms with the assistance of photons.A Duality in DesignWhile this current quantum photonic circuit leverages photons as mediators for interactions between the synthetic atoms (or qubits), the photons themselves can also act as different qubits within the system.” The circuit can indeed work for 2 purposes,” Sun elaborated. “By embedding synthetic atoms inside a photonic quantum circuit, we can use the artificial atoms as sources and memories of single photons, possibly reducing the resource required to build a photonic quantum processor.” The combination of the product compatibility and the duality of the qubits in the system recommends that Suns circuit design could have huge implications for the future of quantum info, offering a reliable way to scale up the incorporated quantum photonic systems.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.3 c02645.
