Quantum memory

Quantum memory based on the quantum exchange to store photon qubits has been demonstrated to be possible. Kessel and Moiseev[3] discussed quantum storage in the single photon state in 1993. The experiment was analyzed in 1998 and demonstrated in 2003. In summary, the study of quantum storage in the single photon state can be regarded as the product of the classical optical data storage technology proposed in 1979 and 1982, an idea inspired by the high density of data storage in the mid-1970s^{[citation needed]}. Optical data storage can be achieved by using absorbers to absorb different frequencies of light, which are then directed to beam space points and stored.

Types

Atomic Gas Quantum Memory

Normal, classical optical signals are transmitted by varying the amplitude of light. In this case, a piece of paper, or a computer hard disk, can be used to store information on the lamp^{[clarification needed]}. In the quantum information scenario, however, the information may be encoded according to the amplitude and phase of the light. For some signals, you cannot measure both the amplitude and phase of the light without interfering with the signal. To store quantum information, light itself needs to be stored without being measured. An atomic gas quantum memory is recording the state of light into the atomic cloud. When light's information is stored by atoms, relative amplitude and phase of light is mapped to atoms and can be retrieved on-demand.^[4]

Solid Quantum Memory

In

Discovery

Optical quantum memory is usually used to detect and store single photon quantum states. However, producing efficient memory of this kind is still a huge challenge for current science. A single photon is so low in energy as to be lost in a complex light background. These problems have long kept quantum storage rates below 50%. A team led by professor Du Shengwang of the department of physics at the Hong Kong University of science and technology

Optical data storage has been an important research topic for many years. Its most interesting function is the use of the laws of quantum physics to protect data from theft, through quantum computing and quantum cryptography unconditionally guaranteed communication security.^[9]

They allow particles to be superimposed and in a superposition state, which means they can represent multiple combinations at the same time. These particles are called quantum bits, or qubits. From a cybersecurity perspective, the magic of qubits is that if a hacker tries to observe them in transit, their fragile quantum states shatter. This means it is impossible for hackers to tamper with network data without leaving a trace. Now, many companies are taking advantage of this feature to create networks that transmit highly sensitive data. In theory, these networks are secure.^[10]

Microwave storage and light learning microwave conversion

The nitrogen-vacancy center in diamond has attracted a lot of research in the past decade due to its excellent performance in optical nanophotonic devices. In a recent experiment, electromagnetically induced transparency was implemented on a multi-pass diamond chip to achieve full photoelectric magnetic field sensing. Despite these closely related experiments, optical storage has yet to be implemented in practice. The existing nitrogen-vacancy center (negative charge and neutral nitrogen-vacancy center) energy level structure makes the optical storage of the diamond nitrogen-vacancy center possible.

The coupling between the nitrogen-vacancy spin ensemble and superconducting qubits provides the possibility for microwave storage of superconducting qubits. Optical storage combines the coupling of electron spin state and superconducting quantum bits, which enables the nitrogen-vacancy center in diamond to play a role in the hybrid quantum system of the mutual conversion of coherent light and microwave.^[11]

Orbital angular momentum is stored in alkali vapor

Large resonant light depth is the premise of constructing efficient quantum-optical memory. Alkali metal vapor isotopes of a large number of near-infrared wavelength optical depth, because they are relatively narrow spectrum line and the number of high density in the warm temperature of 50-100 ∘ C. Alkali vapors have been used in some of the most important memory developments, from early research to the latest results we are discussing, due to their high optical depth, long coherent time and easy near-infrared optical transition.

Because of its high information transmission ability, people are more and more interested in its application in the field of quantum information. Structured light can carry orbital angular momentum, which must be stored in the memory to faithfully reproduce the stored structural photons. An atomic vapor quantum memory is ideal for storing such beams because the orbital angular momentum of photons can be mapped to the phase and amplitude of the distributed integration excitation. Diffusion is a major limitation of this technique because the motion of hot atoms destroys the spatial coherence of the storage excitation. Early successes included storing weakly coherent pulses of spatial structure in a warm, ultracold atomic whole. In one experiment, the same group of scientists in a caesium magneto-optical trap was able to store and retrieve vector beams at the single-photon level.^[12] The memory preserves the rotation invariance of the vector beam, making it possible to use it in conjunction with qubits encoded for maladjusted immune quantum communication.

The first storage structure, a real single photon, was achieved with electromagnetically induced transparency in rubidium magneto-optical trap. The predicted single photon generated by spontaneous four-wave mixing in one magneto-optical trap is prepared by an orbital angular momentum unit using spiral phase plates, stored in the second magneto-optical trap and recovered. The dual-orbit setup also proves coherence in multimode memory, where a preannounced single photon stores the orbital angular momentum superposition state for 100 nanoseconds.^[11]

GEM

GEM (Gradient Echo Memory) is a protocol for storing optical information and it can be applied to both atomic gas and solid-state memories. The idea was first demonstrated by researchers at

Electromagnetically induced transparency (EIT) was first introduced by Harris and his colleagues at

Nevertheless, diamond memory has allowed some revealing studies of the interactions between light and matter at the quantum level: optical phonons in a diamond can be used to demonstrate emission quantum memory, macroscopic entanglement, pre-predicted single-photon storage, and single-photon frequency manipulation.[11]

Future development

For quantum memory, quantum communication and cryptography are the future research directions. However, there are many challenges to building a global quantum network. One of the most important challenges is to create memories that can store the quantum information carried by light. Researchers at the

• Qubit
• Quantum
• Quantum computing
• Quantum information science

References