Metamaterials, artificially structured electromagnetic (EM) materials, have enabled the realization of many unconventional EM properties not found in nature, such as negative refractive index, magnetic response, invisibility cloaking, and so on. Based on these man-made materials with novel EM properties, various devices are designed and realized. However, quantum analog devices based on metamaterials have not been achieved so far. Here, metamaterials are designed and printed to perform quantum search algorithm. The structures, comprising of an array of 2D subwavelength air holes with different radii perforated on the dielectric layer, are fabricated using a 3D-printing technique. When an incident wave enters in the designed metamaterials, the profile of beam wavefront is processed iteratively as it propagates through the metamaterial periodically. After ≈N roundtrips, precisely the same as the efficiency of quantum search algorithm, searched items will be found with the incident wave all focusing on the marked positions. Such a metamaterial-based quantum searching simulator may lead to remarkable achievements in wave-based signal processors.
Metamaterials, artificially structured electromagnetic (EM) materials, have enabled the realization of many unconventional EM properties not found in nature, such as negative refractive index, magnetic response, invisibility cloaking, and so on. Based on these man-made materials with novel EM properties, various devices are designed and realized. However, quantum analog devices based on metamaterials have not been achieved so far. Here, metamaterials are designed and printed to perform quantum search algorithm. The structures, comprising of an array of 2D subwavelength air holes with different radii perforated on the dielectric layer, are fabricated using a 3D-printing technique. When an incident wave enters in the designed metamaterials, the profile of beam wavefront is processed iteratively as it propagates through the metamaterial periodically. After ≈N roundtrips, precisely the same as the efficiency of quantum search algorithm, searched items will be found with the incident wave all focusing on the marked positions. Such a metamaterial-based quantum searching simulator may lead to remarkable achievements in wave-based signal processors.
Metamaterials are artificially engineered periodic structures with exceptional optical properties that are not found in conventional materials. However, this definition of metamaterials can be extended if we introduce a quantum degree of freedom by adding some quantum elements (e.g quantum dots, cold atoms, Josephson junctions, molecules). Quantum metamaterials can then be defined as artificially engineered nanostructures made up of quantum elements. Furthermore, they exhibit controllable quantum states, maintain quantum coherence for times much higher than the transversal time of the electromagnetic signal. Metamaterials have been used to realised invisibility cloaking, super-resolution, energy harvesting, and sensing. Most of these applications are performed in the classical regime. Of recent, metamaterials have gradually found their way into the quantum regime, particularly to quantum sensing and quantum information processing. The use of quantum metamaterials for quantum information processing is still new and rapidly growing. In quantum information processing, quantum metamaterials have enabled the control and manipulation of quantum states, single photon generation, creating quantum entanglement, quantum states switching, quantum search algorithm, quantum state engineering tasks, and many more. In this work, we briefly review the theory, fabrication and applications of quantum metamaterials to quantum information processing.
Optical analog computing has natural advantages of parallel computation, high speed and low energy consumption over traditional digital computing. To date, research in the field of on-chip optical analog computing has mainly focused on classical mathematical operations. Despite the advantages of quantum computing, on-chip quantum analog devices based on metasurfaces have not been demonstrated so far. In this work, based on a silicon-on-insulator (SOI) platform, we illustrated an on-chip quantum searcher with a characteristic size of 60 × 20 μm2. We applied classical waves to simulate the quantum search algorithm based on the superposition principle and interference effect, while combining it with an on-chip metasurface to realize modulation capability. The marked items are found when the incident waves are focused on the marked positions, which is precisely the same as the efficiency of the quantum search algorithm. The proposed on-chip quantum searcher facilitates the miniaturization and integration of wave-based signal processing systems.
During the past few years, a lot of efforts have been devoted in studying optical analog computing with artificial structures. Up to now, much of them are primarily focused on classical mathematical operations. How to use artificial structures to simulate quantum algorithm is still to be explored. In this work, an all-dielectric metamaterial-based model is proposed and realized to demonstrate the quantum Deutsch-Jozsa algorithm. The model is comprised of two cascaded functional metamaterial subblocks. The oracle subblock encodes the detecting functions (constant or balanced), onto the phase distribution of the incident wave. Then, the original Hadamard transformation is performed with a graded-index subblock. Both the numerical and experimental results indicate that the proposed metamaterials are able to simulate the Deutsch-Jozsa problem with one round operation and a single measurement of the output eletric field, where the zero (maximum) intensity at the central position results from the destructive (constructive) interference accompanying with the balance (constant) function marked by the oracle subblock. The proposed computational metamaterial is miniaturized and easy-integration for potential applications in communication, wave-based analog computing, and signal processing systems.
Metamaterials are a class of artificially engineered materials with periodic structures possessing exceptional properties not found in conventional materials. This definition can be extended when we introduce a degree of freedom by adding quantum elements such as quantum dots, cold atoms, Josephson junctions, and molecules, making metamaterials highly valuable for various quantum applications. Metamaterials have been used to achieve invisibility cloaking, super-resolution, energy harvesting, and sensing, among other applications. Most of these applications are performed in the classical regime. Metamaterials have gradually made their way into the quantum regime since the advent of quantum computing and quantum sensing and imaging. Quantum metamaterials are a relatively new technology, and their use in quantum information processing has proliferated. We restrict this study to quantum state manipulation and control, quantum entanglement, single photon generation, quantum state switching, quantum state engineering, quantum key distribution, quantum algorithms, orbital angular momentum, and quantum imaging. Considering these developments, we examine the theory, fabrication, and applications contributing to quantum information processing and how quantum metamaterials contribute to this field. We find that the ability to harness the unique properties of metamaterials to drive these applications is of great importance, as they have the potential to unlock new possibilities for revolutionizing quantum information processing, bringing the world closer to practical quantum technologies with unprecedented capabilities. We conclude by suggesting possible future research directions.
Metamaterials have been a major research area for more than two decades now, involving artificial structures with predesigned electromagnetic properties constructed from deep subwavelength building blocks. They have been used to demonstrate a wealth of fascinating phenomena ranging from negative refractive index and epsilon-near-zero to cloaking, emulations of general relativity effects, and super-resolution imaging, to name a few. In the past few years, metamaterials have been suggested as a new platform for quantum optics, and several pioneering experiments have already been carried out with single photons. Here, we employ a dielectric metasurface to generate entanglement between spin and orbital angular momentum of single photons. We demonstrate experimentally the generation of the four Bell states by utilizing the geometric phase arising from the photonic spin-orbit interaction. These are the first experiments with entangled states with metasurfaces, and as such they are paving the way to the new area of quantum metamaterials.
Quantum metamaterials extend the concept of metamaterials to the case where an artificial optical (in the broad sense) medium can maintain global quantum coherence over times exceeding the traversal time of an electromagnetic signal and the quantum states of their building blocks can be externally controlled. So far 1D and 2D quantum metamaterials have been contemplated. Here we discuss the possible realizations of a 3D quantum metamaterial based on a network on current-biased Josephson junctions (phase qubits).