placeholder for Literature Review - Physical System of Quantum Memory from Research Progress Report _ for PhD Candidature Defence_28May2023

 

Atomic Ensembles:

• Cold Atomic Gases: Cold atomic gases, such as ultra-cold rubidium or caesium gases, have been used as quantum memory systems. These systems rely on techniques like Electromagnetically-Induced Transparency (EIT) to achieve long-lived storage and retrieval of quantum information.
• Rare-Earth Ions: Ensembles of rare-earth ions, embedded in a solid matrix such as a crystal, have shown potential for quantum memory applications. These ions can be coupled to optical cavities to enhance the storage and retrieval of quantum states.

Solid-State Systems:

• Rare-Earth Doped Crystals: Crystals doped with rare-earth ions, such as europium or praseodymium, have been explored as solid-state quantum memory systems. These systems offer the advantage of long coherence times and can be interfaced with photons for information transfer.
• Semiconductor Quantum Dots: Semiconductor quantum dots, which are tiny nanostructures, have shown promise as solid-state quantum memories. By controlling the electronic and optical properties of quantum dots, researchers aim to achieve efficient storage and retrieval of quantum information.
• Superconducting Circuits: Superconducting circuits, composed of Josephson junctions and other superconducting elements, have been investigated for quantum memory applications. These circuits can store quantum information in the form of superconducting qubits and achieve long coherence times.

Photonic Quantum Memory:

• Atomic or Molecular Systems: Photons can be stored in atomic or molecular systems using techniques like EIT or off-resonant Raman scattering. These systems allow for the delay and retrieval of optical signals with quantum information.
• Nonlinear Optical Materials: Certain nonlinear optical materials, such as rare-earth-doped crystals or quantum dots, can be used for photonic quantum memory. By exploiting the nonlinear properties of these materials, researchers aim to achieve efficient storage and retrieval of quantum states encoded in photons.
• Photonic Structures:Photonic structures refer to a variety of optical devices and components that facilitate the storage and retrieval of quantum information encoded in photons. These structures include but are not limited to Microring Resonators, which are optical devices composed of high-quality materials like silicon or silicon nitride. Photonic structures provide a platform for efficient light-matter interactions, enabling the storage of quantum information in the circulating modes or waveguide structures. These structures possess specific optical properties, such as high finesse and strong confinement of light, which contribute to the preservation of coherence and enhance the storage and retrieval efficiency. Photonic structures, including Microring Resonators, play a crucial role in realizing photonic quantum memory by enabling the delay and retrieval of optical signals carrying quantum information. In addition to Microring Resonators, there are several other examples of photonic structures used in the field of photonic quantum memory. These structures are designed to manipulate and control the interaction between light and matter, enabling efficient storage and retrieval of quantum information. Here are some other examples:

·        Photonic Crystal Cavities: Photonic crystal cavities are engineered structures that can confine light to small volumes by creating a periodic modulation of the refractive index. These cavities provide strong light-matter interaction and have been used for the storage and retrieval of quantum information.

·        Bragg Gratings: Bragg gratings are periodic structures consisting of alternating layers with different refractive indices. They can control the propagation of light by reflecting certain wavelengths and transmitting others. Bragg gratings have been employed in the field of photonic quantum memory for efficient manipulation of photons.

·        Optical Fiber Networks: Optical fibers can be used as photonic structures for quantum memory applications. By creating specialized fiber networks with specific properties, such as long coherence times and low loss, quantum information can be stored and transmitted over long distances.

·        Photonic Waveguides: Photonic waveguides are structures that guide and confine light, enabling efficient transfer of photons in quantum memory systems. Different types of waveguides, such as straight waveguides, bent waveguides, or strip waveguides, can be employed based on the specific requirements of the system.

·        Whispering Gallery Mode Resonators: Whispering gallery mode resonators are spherical or cylindrical structures that confine light using total internal reflection. They have high quality factors and can store photons for relatively long periods of time, making them suitable for applications in photonic quantum memory.

·        Nanophotonic Structures: Nanophotonic structures, such as nanoantennas, nanowires, or nanopillars, provide precise control over light-matter interactions at the nanoscale. These structures offer the potential for highly efficient and compact quantum memory systems.