Studies in Quantum Information Theory
... its emphasis on string theory and for the flexibility and support of the Physics Department, and Carl was with me all the way through this process. When I decided to switch topics to quantum information theory, Carl spoke with Michael (who was his former Ph.D. student) on my behalf and helped me to ...
... its emphasis on string theory and for the flexibility and support of the Physics Department, and Carl was with me all the way through this process. When I decided to switch topics to quantum information theory, Carl spoke with Michael (who was his former Ph.D. student) on my behalf and helped me to ...
QUANTUM MECHANICS • Introduction : Quantum Mechanics with
... with a NOT gate we predict that it will become a down (and then we can measure it to confirm that our prediction is true). What about a quantum two-state system? Such a quantum state is called a qubit, for “quantum bit” obviously. What are the properties of a qubit and what kind of real physical sys ...
... with a NOT gate we predict that it will become a down (and then we can measure it to confirm that our prediction is true). What about a quantum two-state system? Such a quantum state is called a qubit, for “quantum bit” obviously. What are the properties of a qubit and what kind of real physical sys ...
Quantum Reflection at Strong Magnetic Fields
... the self-interactions of electromagnetic fields by means of induced electron-positron pairs are, for example, light-by-light scattering [9] and photon splitting [10]. Conceptionally, all of these signatures differ in the order to which the microscopic photon field f µν couples to the virtual electro ...
... the self-interactions of electromagnetic fields by means of induced electron-positron pairs are, for example, light-by-light scattering [9] and photon splitting [10]. Conceptionally, all of these signatures differ in the order to which the microscopic photon field f µν couples to the virtual electro ...
Entanglement and state characterisation from two-photon interference
... the double-slit experiment designed by Thomas Young demonstrated the validity of the wave theory of light and of the superposition principle for light waves. About a century later, the wave-particle duality introduced to explain quantum effects put interference and the superposition principle back a ...
... the double-slit experiment designed by Thomas Young demonstrated the validity of the wave theory of light and of the superposition principle for light waves. About a century later, the wave-particle duality introduced to explain quantum effects put interference and the superposition principle back a ...
Monday, Apr. 4, 2005
... – Wave function ( )is the probability distribution function of a quantum state at any given space-time coordinates – The observable is invariant or conserved if the operator Q commutes with Hamiltonian Monday, Apr. 4, 2005 ...
... – Wave function ( )is the probability distribution function of a quantum state at any given space-time coordinates – The observable is invariant or conserved if the operator Q commutes with Hamiltonian Monday, Apr. 4, 2005 ...
![Theoretical Physics II B – Quantum Mechanics [1cm] Lecture 8](http://s1.studyres.com/store/data/004850917_1-fa2fc63a7feab663fd3f9ddfe650a8b4-300x300.png)
CHAPTER 23 The Interaction of Light with Matter: I
... If λ ≫ λC such a shift is negligble, and we are in the regime that is well described by Thomson scattering. Compton scattering is a quantum-mechanical process. The quantum aspect also influences the actual cross section, which changes from the Thomson cross section, σT , at the low-frequency end, to ...
... If λ ≫ λC such a shift is negligble, and we are in the regime that is well described by Thomson scattering. Compton scattering is a quantum-mechanical process. The quantum aspect also influences the actual cross section, which changes from the Thomson cross section, σT , at the low-frequency end, to ...
Physical Entanglement in Permutation
... joint Hilbert space; and our best understanding of permutation invariance is one in which factor Hilbert space indices—or, equivalently, the order in which they stand in the tensor product—have no physical meaning. The second and third biconditionals will drop out of a proper revision of these conce ...
... joint Hilbert space; and our best understanding of permutation invariance is one in which factor Hilbert space indices—or, equivalently, the order in which they stand in the tensor product—have no physical meaning. The second and third biconditionals will drop out of a proper revision of these conce ...
Aspects of the Quantum Hall Effect
... one edge to the other, thereby making it possible to do work against a potential gradient in a direction transverse to the electric current induced by the changing flux. This gives rise to a Hall conductance quantized at integer values. These arguments hold quite generally – immune to details of the ...
... one edge to the other, thereby making it possible to do work against a potential gradient in a direction transverse to the electric current induced by the changing flux. This gives rise to a Hall conductance quantized at integer values. These arguments hold quite generally – immune to details of the ...
Constructor theory of information - Proceedings of the Royal Society A
... Information is also of the essence in preparation and measurement, both of which are necessary for testing scientific theories. The output of a measurement is information; the input of a preparation includes information, specifying an attribute with which a physical system is to be prepared. All thes ...
... Information is also of the essence in preparation and measurement, both of which are necessary for testing scientific theories. The output of a measurement is information; the input of a preparation includes information, specifying an attribute with which a physical system is to be prepared. All thes ...
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.