single photon
... probably only occur via removing a whole wave – train. Shortening a wave-train is improbable since that would have an effect of attenuation on temporal coherence, which has so far not yet been observed. In the lower panel the energy per optical cycle is an integer multiple of hν. This can be probabl ...
... probably only occur via removing a whole wave – train. Shortening a wave-train is improbable since that would have an effect of attenuation on temporal coherence, which has so far not yet been observed. In the lower panel the energy per optical cycle is an integer multiple of hν. This can be probabl ...
Quantum Computers - Computing Sciences
... The essence of quantum cryptography is a way of transmitting a cryptography key without allowing anyone else to listen on the line. Because of the nature of quantum superposition, if a spy was measuring the key while it was being transmitted, the receiver would be able to tell that someone else had ...
... The essence of quantum cryptography is a way of transmitting a cryptography key without allowing anyone else to listen on the line. Because of the nature of quantum superposition, if a spy was measuring the key while it was being transmitted, the receiver would be able to tell that someone else had ...
Lecture 5
... n qubits initialized with the input (classical state) s qubits workspace At all times there is a global state on n+s qubitts Unitary operations (on 1, 2, or 3 qubits) U1,…,UT; given together with choice of the qubits Applying operation Ui : take the tensor product with the identity on the other qubi ...
... n qubits initialized with the input (classical state) s qubits workspace At all times there is a global state on n+s qubitts Unitary operations (on 1, 2, or 3 qubits) U1,…,UT; given together with choice of the qubits Applying operation Ui : take the tensor product with the identity on the other qubi ...
Chapter 5
... a natural question to ask would be whether we can tell which slit a photon pass through. Modified Experiment: A LASER ...
... a natural question to ask would be whether we can tell which slit a photon pass through. Modified Experiment: A LASER ...
example: on the Bloch sphere: this is a rotation around the equator
... comparison with classical gates: - XOR is not reversible - CNOT is reversible (unitary) Universality of controlled NOT: Any multi qubit logic gate can be composed of CNOT gates and single qubit gates X,Y,Z. ...
... comparison with classical gates: - XOR is not reversible - CNOT is reversible (unitary) Universality of controlled NOT: Any multi qubit logic gate can be composed of CNOT gates and single qubit gates X,Y,Z. ...
Introduction to Quantum Statistics
... (ideally an infinite number of identically prepared quantum systems) using density operators. This description was completely sufficient for the first 60 years of the existence of quantum mechanics because it was generally regarded as completely impossible to observe and manipulate single-quantum sy ...
... (ideally an infinite number of identically prepared quantum systems) using density operators. This description was completely sufficient for the first 60 years of the existence of quantum mechanics because it was generally regarded as completely impossible to observe and manipulate single-quantum sy ...
Here
... know the mathematical expectation value for this variable, one calculates the Ψ-function for this later moment from the “time-dependent wave equation”. Then one applies the corresponding operator, which mentioned above, which is the same for every moment. On the other side the q-number-theorist has ...
... know the mathematical expectation value for this variable, one calculates the Ψ-function for this later moment from the “time-dependent wave equation”. Then one applies the corresponding operator, which mentioned above, which is the same for every moment. On the other side the q-number-theorist has ...
Document
... in neat orbits, cannot be correct. Quantum theory describes an electron probability distribution: ...
... in neat orbits, cannot be correct. Quantum theory describes an electron probability distribution: ...
chapter-12 quantum entanglement
... The EPR paper emphasizes on the distinction between the objective reality (which should be independent of any theory) and the physical concepts with which a given theory operates The concepts are intended to correspond with the objective reality, and by means of these concepts we picture this real ...
... The EPR paper emphasizes on the distinction between the objective reality (which should be independent of any theory) and the physical concepts with which a given theory operates The concepts are intended to correspond with the objective reality, and by means of these concepts we picture this real ...
Quantum key distribution
Quantum key distribution (QKD) uses quantum mechanics to guarantee secure communication. It enables two parties to produce a shared random secret key known only to them, which can then be used to encrypt and decrypt messages. It is often incorrectly called quantum cryptography, as it is the most well known example of the group of quantum cryptographic tasks.An important and unique property of quantum key distribution is the ability of the two communicating users to detect the presence of any third party trying to gain knowledge of the key. This results from a fundamental aspect of quantum mechanics: the process of measuring a quantum system in general disturbs the system. A third party trying to eavesdrop on the key must in some way measure it, thus introducing detectable anomalies. By using quantum superpositions or quantum entanglement and transmitting information in quantum states, a communication system can be implemented which detects eavesdropping. If the level of eavesdropping is below a certain threshold, a key can be produced that is guaranteed to be secure (i.e. the eavesdropper has no information about it), otherwise no secure key is possible and communication is aborted.The security of encryption that uses quantum key distribution relies on the foundations of quantum mechanics, in contrast to traditional public key cryptography which relies on the computational difficulty of certain mathematical functions, and cannot provide any indication of eavesdropping at any point in the communication process, or any mathematical proof as to the actual complexity of reversing the one-way functions used. QKD has provable security based on information theory, and forward secrecy.Quantum key distribution is only used to produce and distribute a key, not to transmit any message data. This key can then be used with any chosen encryption algorithm to encrypt (and decrypt) a message, which can then be transmitted over a standard communication channel. The algorithm most commonly associated with QKD is the one-time pad, as it is provably secure when used with a secret, random key. In real world situations, it is often also used with encryption using symmetric key algorithms like the Advanced Encryption Standard algorithm. In the case of QKD this comparison is based on the assumption of perfect single-photon sources and detectors, that cannot be easily implemented.