dear reader,
Welcome back to our series on Quantum Mechanics. In the previous articles, we have discussed in depth the origin of quantum mechanics, basic concepts, experimental verification and interpretation problems, and the application of quantum computing. Today, we continue to explore two other compelling application areas of quantum mechanics: quantum communication and quantum sensing.
1. Quantum Communication: Quantum Teleportation and Quantum Key Distribution
Quantum communication is the use of the properties of quantum mechanics to achieve safe and efficient information transmission. Among them, quantum teleportation and quantum key distribution are two important quantum communication protocols.
1.1 Quantum teleportation
Quantum teleportation refers to the transfer of a qubit of information from one location to another, rather than through conventional matter or energy transfers. During this transmission process, the qubit information seems to be transmitted instantaneously, which violates the causality law of relativity, but in fact it does not really violate the causality.
At the heart of quantum teleportation is quantum entanglement. By entanglement of two qubits, their states are still correlated even if they are far apart. When the state of one qubit changes, the state of the other qubit changes immediately. Using this entanglement relationship, we can achieve quantum teleportation.
The specific steps of quantum teleportation are as follows:
Create an entangled pair: Alice, the sender, and Bob, the receiver, jointly create a pair of entangled qubits and keep a part of them each.
Transmitting information: Alice performs a series of operations on the qubits to be transmitted and the entangled bits she retains, and measures a set of information.
Passing classical information: Alice sends the measurement result to Bob through a classical channel.
Reconstructing qubits: Bob operates on the entangled bits he retains based on the information received, thereby reconstructing the exact same state as Alice's transmitted qubits.
Through quantum teleportation, qubit information can be transmitted instantaneously in space, and due to the characteristics of quantum entanglement, the transmission process is very sensitive to external interference. Once someone tries to eavesdrop or intercept information, the quantum entanglement will be destroyed immediately, so that communication Both parties immediately noticed the leak of information.
1.2 Quantum key distribution
Quantum key distribution is a quantum communication protocol for secure key distribution. In traditional communication, key distribution often faces the risk of being eavesdropped or attacked. Quantum key distribution utilizes the principles of quantum entanglement and measurement to ensure the secure distribution of keys.
The process of quantum key distribution is as follows:
Create an entangled pair: Alice, the sender, and Bob, the receiver, jointly create a pair of entangled qubits and keep a part of them each.
Qubit transmission: Alice and Bob randomly select a measurement benchmark on each entangled pair and measure the state of the qubit. Due to the properties of quantum entanglement, the measurements are perfectly correlated, even if they are separated by great distances.
Classical communication: Alice and Bob exchange their measurements over a classical channel and disclose which benchmarks they have chosen.
Key extraction: Based on the same measurements and publicly available baseline information, Alice and Bob can extract a consistent key. Due to the properties of quantum entanglement, any eavesdropping on a qubit will be detected immediately.
The security of quantum key distribution is based on the unclonability of quantum entanglement, that is, the information of the quantum state cannot be copied or stolen. Therefore, even if the transmission channel of the communication may have the risk of being eavesdropped, quantum key distribution can ensure the security of the key.
1.3 Application
The Micius quantum communication satellite is the world's first space quantum science experiment satellite independently developed by China. Domain quantum key network experiment and quantum mechanics completeness test and other experimental research. At 1:40 on August 16, 2016, the Micius quantum communication satellite was successfully launched into space, realizing the world's first quantum communication between the satellite and the ground. The establishment of the quantum secure communication and scientific experiment system has been officially completed, which represents an important step in the construction of a global secure communication network by quantum technology.
2. Quantum Sensing: Quantum Measurement and Quantum Sensing
Quantum sensing is the use of quantum measurements and the sensitivity of quantum states for high-precision measurement and sensing. In traditional measurement, the measurement accuracy is subject to some physical limitations, such as the accuracy of the measurement instrument and noise interference. Quantum sensing can overcome these limitations and achieve high-precision measurements by utilizing the superposition and coherence of quantum states.
2.1 Quantum measurement
In traditional measurement, we can use measuring instruments to determine the value of a physical quantity, such as position, momentum, spin, etc. However, the measurement process will cause interference to the quantum state, causing the quantum state to collapse to a definite state after measurement.
Quantum measurements exploit the properties of superposition states. In quantum measurement, we can choose an appropriate measurement benchmark and measure it. Different measurement benchmarks will measure different measurement results, and in the superposition state, we can obtain the probability distribution of all possible measurement results at the same time. This allows quantum measurements to achieve high precision beyond traditional measurements in some cases.
2.2 Quantum Sensing
Quantum sensing exploits the sensitivity of quantum states to small perturbations. In traditional sensing, measuring small disturbances often requires very sophisticated instruments and complex algorithms. In quantum sensing, by utilizing the sensitivity of quantum superposition states, we can achieve high sensitivity to small perturbations.
A classic example is quantum gyroscopes. Traditional gyroscopes use rotating mechanical parts to measure the angular rate of rotation. The quantum gyroscope uses the superposition state and interference phenomenon of qubits to achieve high-precision measurement of the rotational angular velocity, and thus has important applications in the fields of inertial navigation and aerospace.
3. Future Prospects of Quantum Communication and Quantum Sensing
Quantum communication and quantum sensing, as important application areas of quantum mechanics, provide us with a new way of information transmission and measurement. As quantum technologies continue to advance, we can expect safer, more efficient, and more precise communications and measurements.
In the future, quantum communication and quantum sensing will play an important role in the fields of information security, communication network, earth science, biomedicine and navigation. Quantum teleportation of quantum communication can be used for high-security communication and data transmission; quantum key distribution can be used for encrypted communication; quantum sensing can be used for high-precision measurement and detection.
Summarize
As two important application areas of quantum mechanics, quantum communication and quantum sensing provide a new way of information transmission and measurement. Quantum communication utilizes the characteristics of quantum entanglement to realize quantum teleportation and quantum key distribution, realizing safe and efficient information transmission. Quantum sensing utilizes the sensitivity of quantum states to achieve high-precision measurement and sensing, and has important application prospects. With the continuous development of quantum technology, we are full of confidence in the future of quantum communication and quantum sensing, and look forward to them bringing more scientific and technological progress to mankind.
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