Showing papers on "No-teleportation theorem published in 2003"
Journal Article•
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TL;DR: The author describes how such a quantum computer-a computer based on the rules of quantum mechanics-may work, and how it is going to give incredible speed and problem-solving power.
Abstract: Using atoms as digital bits will start a completely new era in computer design. Atoms cannot be simply manipulated and used like the bits built with transistors. The behavior of matter on the atomic scale follows the rules of modern physics. This behavior cannot be understood in terms of our classical description of the world (i. e. Newtonian mechanics or Maxwell's equations in electromagnetics). The physical theory dealing with such behavior is called quantum mechanics. Its use in the computer industry will most probably cause a revolution in the way we use and understand computers. The author describes how such a quantum computer-a computer based on the rules of quantum mechanics-may work, and how it is going to give incredible speed and problem-solving power.
710 citations
TL;DR: Here is a long-distance experimental demonstration of probabilistic quantum teleportation, where qubits are carried by photons and teleported onto photons of 1.3 µm wavelength from one laboratory to another, separated by 55 m but connected by 2 km of standard telecommunications fibre.
Abstract: Matter and energy cannot be teleported (that is, transferred from one place to another without passing through intermediate locations). However, teleportation of quantum states (the ultimate structure of objects) is possible1: only the structure is teleported—the matter stays at the source side and must be already present at the final location. Several table-top experiments have used qubits2,3,4,5,6,7 (two-dimensional quantum systems) or continuous variables8,9,10 to demonstrate the principle over short distances. Here we report a long-distance experimental demonstration of probabilistic quantum teleportation. Qubits carried by photons of 1.3 µm wavelength are teleported onto photons of 1.55 µm wavelength from one laboratory to another, separated by 55 m but connected by 2 km of standard telecommunications fibre. The first (and, with foreseeable technologies, the only) application of quantum teleportation is in quantum communication, where it could help to extend quantum cryptography to larger distances11,12,13.
441 citations
TL;DR: In this paper, the storage and retrieval of an image in a multi-particle quantum mechanical system was investigated and compared with corresponding classical digital methods, where qubits replaced classical bits in an array of pixels and showed several advantages.
Abstract: We investigate the storage and retrieval of an image in a multi-particle quantum mechanical system. Several models are studied and compared with corresponding classical digital methods. We consider a situation in which qubits replace classical bits in an array of pixels and show several advantages. For example, we consider the situation in which 4 different values are randomly stored in a single qubit and show that quantum mechanical properties allow better reproduction of original stored values compared with classical (even stochastic) methods. The retrieval process is uniquely quantum (involves measurement in more than one bases). The independence and the finiteness of the stored copies of the image play an important role in the quantum protocol being better than the classical one. Other advantages of quantum storage of an image are found in its security.
360 citations
TL;DR: It is shown that $2n$ random classical bits are both necessary and sufficient for encrypting any unknown state of n quantum bits in an informationally secure manner and a connection is made between quantum encryption and quantum teleportation that allows for a different proof of optimality of teleportation.
Abstract: We show that $2n$ random classical bits are both necessary and sufficient for encrypting any unknown state of n quantum bits in an informationally secure manner. We also characterize the complete set of optimal protocols in terms of a set of unitary operations that comprise an orthonormal basis in a canonical inner product space. Moreover, a connection is made between quantum encryption and quantum teleportation that allows for a different proof of optimality of teleportation.
340 citations
TL;DR: It is shown that electronic spin coherence can be reversibly mapped onto the collective state of the surrounding nuclei and can be used, when combined with standard resonance techniques, to reversibly store coherent superpositions on the time scale of seconds.
Abstract: We describe a technique to create long-lived quantum memory for quantum bits in mesoscopic systems. Specifically we show that electronic spin coherence can be reversibly mapped onto the collective state of the surrounding nuclei. The coherent transfer can be efficient and fast and it can be used, when combined with standard resonance techniques, to reversibly store coherent superpositions on the time scale of seconds. This method can also allow for "engineering" entangled states of nuclear ensembles and efficiently manipulating the stored states. We investigate the feasibility of this method through a detailed analysis of the coherence properties of the system.
214 citations
TL;DR: In this paper, the authors investigated two schemes of quantum teleportation with a W state, which belongs to a different class from the Greenberger-Horne-Zeilinger class.
Abstract: We investigate two schemes of quantum teleportation with a W state, which belongs to a different class from the Greenberger–Horne–Zeilinger class. In the first scheme, the W state is shared by three parties, one of whom, called a sender, performs a Bell measurement. It is shown that the quantum information of an unknown state is split between two parties and recovered with a certain probability. In the second scheme, a sender takes two particles of the W state and performs positive operator valued measurements. For the two schemes, we calculate the success probability and the average fidelity. We show that the average fidelity of the second scheme cannot exceed that of the first one.
213 citations
TL;DR: An optical scheme to communicate classical bits without a shared reference frame using entangled photon pairs and linear optical Bell state measurements is presented.
Abstract: We show that communication without a shared reference frame is possible using entangled states. Both classical and quantum information can be communicated with perfect fidelity without a shared reference frame at a rate that asymptotically approaches one classical bit or one encoded qubit per transmitted qubit. We present an optical scheme to communicate classical bits without a shared reference frame using entangled photon pairs and linear optical Bell state measurements.
157 citations
TL;DR: It is well known that entanglement on its own is useless for the transmission of information, but there are distributed tasks that cannot be accomplished at all in a classical world when communication is not allowed, but that become possible if the non-communicating parties share prior entanglements.
Abstract: Can quantum communication be more efficient than its classical counterpart? Holevo's theorem rules out the possibility of communicating more than n bits of classical information by the transmission of n quantum bits—unless the two parties are entangled, in which case twice as many classical bits can be communicated but no more. In apparent contradiction, there are distributed computational tasks for which quantum communication cannot be simulated efficiently by classical means. In some cases, the effect of transmitting quantum bits cannot be achieved classically short of transmitting an exponentially larger number of bits. In a similar vein, can entanglement be used to save on classical communication? It is well known that entanglement on its own is useless for the transmission of information. Yet, there are distributed tasks that cannot be accomplished at all in a classical world when communication is not allowed, but that become possible if the non-communicating parties share prior entanglement. This leads to the question of how expensive it is, in terms of classical communication, to provide an exact simulation of the spooky power of entanglement.
149 citations
TL;DR: In this paper, the authors introduce a protocol for quantum secret sharing based on reusable entangled states, where the entangled state between the sender and the receiver acts only as a carrier to which data bits are entangled by the sender, and disentangled from it by the receivers.
Abstract: We introduce a protocol for quantum secret sharing based on reusable entangled states. The entangled state between the sender and the receiver acts only as a carrier to which data bits are entangled by the sender and disentangled from it by the receivers, all by local actions of simple gates. We also show that the interception by Eve or the cheating of one of the receivers introduces a quantum bit error rate larger than 25% which can be detected by comparing a subsequence of the bits.
141 citations
TL;DR: In this paper, a scheme for teleporting an arbitrary three-particle state is proposed when three pairs of entangled particles are used as quantum channels and the probability of successful teleportation is determined by the smallest coefficients of the three entangled pairs.
Abstract: A scheme for teleporting an arbitrary three-particle state is proposed when three pairs of entangled particles are used as quantum channels. Quantum teleportation can be successfully realized with a certain probability if the receiver adopts an appropriate unitary-reduction strategy. The probability of successful teleportation is determined by the smallest coefficients of the three entangled pairs.
134 citations
TL;DR: The basic idea is to suppress unwanted coincidence detection events by providing the photon to be teleported much less frequently than the auxiliary entangled pair, and the experimental fidelity of the procedure surpasses the theoretical limit required for the implementation of quantum repeaters.
Abstract: Quantum teleportation1 is central to quantum communication, and plays an important role in a number of quantum computation protocols2,3. Most information-processing applications of quantum teleportation include the subsequent manipulation of the qubit (the teleported photon), so it is highly desirable to have a teleportation procedure resulting in high-quality, freely flying qubits. In our previous teleportation experiment4, the teleported qubit had to be detected (and thus destroyed) to verify the success of the procedure. Here we report a teleportation experiment that results in freely propagating individual qubits. The basic idea is to suppress unwanted coincidence detection events by providing the photon to be teleported much less frequently than the auxiliary entangled pair. Therefore, a case of successful teleportation can be identified with high probability without the need actually to detect the teleported photon. The experimental fidelity of our procedure surpasses the theoretical limit required for the implementation of quantum repeaters5,6.
TL;DR: In this paper, the authors analyze the case where the quantum channel corresponds to a non-maximally entangled state and show that the success of the protocol is directly related to the problem of distinguishing nonorthogonal quantum states.
Abstract: Quantum teleportation of qudits is revisited. In particular, we analyze the case where the quantum channel corresponds to a nonmaximally entangled state and show that the success of the protocol is directly related to the problem of distinguishing nonorthogonal quantum states. The teleportation channel can be seen as a coherent superposition of two channels, one of them being a maximally entangled state, thus leading to perfect teleportation, and the other, corresponding to a nonmaximally entangled state living in a subspace of the d-dimensional Hilbert space. The second channel leads to a teleported state with reduced fidelity. We calculate the average fidelity of the process and show its optimality.
TL;DR: A proof of the Kochen-Specker theorem for a single two-level system using five eight-element positive operator-valued measures and simple algebraic reasoning based on the geometry of the dodecahedron is presented.
Abstract: A proof of the Kochen-Specker theorem for a single two-level system is presented. It employs five eight-element positive operator-valued measures and a simple algebraic reasoning based on the geometry of the dodecahedron.
TL;DR: It is shown that a qubit can be used to substitute for a classical analog system requiring an arbitrarily large number of classical bits to represent digitally and no finite amount of one-way classical communication can perfectly simulate the effect of quantum entanglement.
Abstract: We show that a qubit can be used to substitute for an arbitrarily large number of classical bits. We consider a physical system S interacting locally with a classical field '(x) as it travels directly from point A to point B. Our task is to use S to answer a simple yes/no question about '(x). If S is a qubit, the task can be done perfectly. On the other hand, if S is a classical system then we show that it must carry an arbitrarily large amount of classical information. We identify the physical reason for such a huge quantum advantage, and show that it also implies a large difference between the size of quantum and classical memories necessary for some computations. We also present a simple proof that no finite amount of one-way classical communication can perfectly simulate the effect of quantum entanglement. A general pure state of a two-level quantum system – a qubit – can be written as a|0i + b|1i , (1) where a and b are complex numbers satisfying |a| 2 + |b| 2 = 1. In general, in order to specify these continuous parameters to arbitrary accuracy we need an arbitrarily large number of classical bits of information. This unbounded amount of information contained in a single state would seem to suggest that a qubit could be used to communicate an arbitrarily large amount of information. Of course, this turns out not to be possible: Holevo’s bound [1] implies that a single qubit cannot be used to transmit more than one bit of information between two previously unentangled parties. This raises doubts about the objective existence of the information encoded in the continuous parameters in (1). In this paper we show how this large amount of information can be used in an information processing task. The trick is not to require that this information can actually be read out, but rather to use it to substitute for a large amount of classical information. We illustrate this with a very simple information processing task which can be performed perfectly with a single qubit but would require an arbitrarily large amount of
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IBM1
TL;DR: In this article, a method for keeping two classical bits hidden in any such scenario can be used to construct a method of keeping one quantum bit hidden, and vice-versa.
Abstract: Recent work has shown how to use the laws of quantum mechanics to keep classical and quantum bits secret in a number of different circumstances. Among the examples are private quantum channels, quantum secret sharing and quantum data hiding. In this paper we show that a method for keeping two classical bits hidden in any such scenario can be used to construct a method for keeping one quantum bit hidden, and vice–versa. In the realm of quantum data hiding, this allows us to construct bipartite and multipartite hiding schemes for qubits from the previously known constructions for hiding bits.
TL;DR: The statistical state of any (classical or quantum) system with nontrivial time evolution can be interpreted as the pointer of a clock and it is shown that this principle, formalized by a quasi-order, implies constraints on many physical processes.
Abstract: The statistical state of any (classical or quantum) system with nontrivial time evolution can be interpreted as the pointer of a clock. The quality of such a clock is given by the statistical distinguishability of its states at different times. If a clock is used as a resource for producing another one the latter can at most have the quality of the resource. We show that this principle, formalized by a quasi-order, implies constraints on many physical processes. Similarly, the degree to which two (quantum or classical) clocks are synchronized can be formalized by a quasi-order of synchronism. Copying timing information is restricted by quantum no-cloning and no-broadcasting theorems since classical clocks can only exist in the limit of infinite energy. We show this quantitatively by comparing the Fisher timing information of two output systems to the input's timing information. For classical signal processing in the quantum regime our results imply that a signal looses its localization in time if it is amplified and distributed to many devices.
TL;DR: By using the Holevo-Schumacher-Westmoreland theorem and through solving eigenvalues of states out from the quantum noisy channels directly, or with the help of the Bloch sphere representation, or Stokes parametrization representation, this paper investigated the classical information capacities of some well-known quantum noisy channel.
Abstract: By using the Holevo–Schumacher–Westmoreland theorem and through solving eigenvalues of states out from the quantum noisy channels directly, or with the help of the Bloch sphere representation, or Stokes parametrization representation, we investigate the classical information capacities of some well-known quantum noisy channels.
TL;DR: This work presents simplification schemes for probabilistic and controlled teleportation of the unknown quantum states of both one particle and two particles and construct efficient quantum logic networks for implementing the new schemes by means of the primitive operations consisting of single-qu bit gates, two-qubit controlled-not gates, Von Neumann measurement, and classically controlled operations.
Abstract: We present simplification schemes for probabilistic and controlled teleportation of the unknown quantum states of both one-particle and two-particle and construct efficient quantum logic networks for implementing the new schemes by means of the primitive operations consisting of single-qubit gates, two-qubit controlled-not gates, Von Neumann measurement and classically controlled operations. In these schemes the teleportation are not always successful but with certain probability.
TL;DR: Based on the quantum networks, it is shown that after the partially entangled states are concentrated into maximal entanglement, the above three kinds of probabilistic teleportation are the same as the standard teleportation using the corresponding maximally entangled states as the quantum channels.
Abstract: By means of the primitive operations consisting of single-qubit gates, two-qubit controlled-not gates, Von Neuman measurement and classically controlled operations, we construct efficient quantum logic networks for implementing probabilistic teleportation of a single qubit, a two-particle entangled state and an N-particle entanglement. Based on the quantum networks, we show that after the partially entangled states are concentrated into maximal entanglement, the above three kinds of probabilistic teleportation are the same as the standard teleportation using the corresponding maximally entangled states as the quantum channels.
TL;DR: It is shown that Trugenberger's scheme is no better than one where the quantum register is replaced with a classical one of equal size and that the Holevo bound and more recent bounds on "quantum random access codes" pretty much rule out powerful memories based on quantum states.
Abstract: This is a comment on two wrong Phys. Rev. Letters papers by C.A. Trugenberger. Trugenberger claimed that quantum registers could be used as exponentially large "associative" memories. We show that his scheme is no better than one where the quantum register is replaced with a classical one of equal size.
We also point out that the Holevo bound and more recent bounds on "quantum random access codes" pretty much rule out powerful memories (for classical information) based on quantum states.
TL;DR: It is speculated what quantum information protocols can be implemented between two accelerating observers using the vacuum, and unconditionally secure coin flipping seems possible but not teleportation.
Abstract: We speculate what quantum information protocols can be implemented between two accelerating observers using the vacuum. Whether it is in principle possible or not to implement a protocol depends on whether the aim is to end up with classical information or quantum information. Thus, unconditionally secure coin flipping seems possible but not teleportation.
TL;DR: In this article, the fidelity of one-and two-photon superposition states based on EPR entanglement of continuous-wave two-mode squeezed state is discussed.
Abstract: Quantum teleportation of one- and two-photon superposition states based on EPR entanglement of continuous-wave two-mode squeezed state is discussed. The fidelities of teleportation are deduced for two different input quantum states. The dependence of the fidelity on the parameters of EPR entanglement and the gain of the classical channels are shown numerically. Comparing with the teleportation of Fock state and coherent state, it is pointed out that for given EPR entanglement and classical gain, the higher the nonclassicality of the input state, the lower the accessible fidelity of teleportation.
Posted Content•
TL;DR: In this paper, the concept of coherent classical communication was introduced and used to relate other resources in quantum information theory, such as super-dense coding to prepare arbitrary quantum states instead of only classical messages.
Abstract: We introduce the concept of coherent classical communication and use it to relate other resources in quantum information theory. Using coherent classical communication, we are able to generalize super-dense coding to prepare arbitrary quantum states instead of only classical messages. We also derive single-letter formulae for the classical and quantum capacities of a bipartite unitary gate assisted by an arbitrary fixed amount of entanglement per use.
Posted Content•
TL;DR: Two protocols for teleportation that require only one classical bit are presented, using an entangled pair of particles and the use of two classical bits of information.
Abstract: The standard protocol for teleportation of a quantum state requires an entangled pair of particles and the use of two classical bits of information. Here, we present two protocols for teleportation that require only one classical bit. In the first protocol, chained XOR operations are performed on the particles before one of them is removed to the remote location where the state is being teleported. In the second protocol, three entangled particles are used.
Posted Content•
TL;DR: A partial answer to the question `in what sense does information gain increase with initial uncertainty?' is provided by showing that, for classical and quantum measurements which are symmetric with respect to reversible transformations of the state space, the information gain regarding the initial state always increases with the observer's initial uncertainty.
Abstract: The information provided by a classical measurement is unambiguously determined by the mutual information between the output results and the measured quantity. However, quantum mechanically there are at least two notions of information gathering which can be considered, one characterizing the information provided about the initial preparation, useful in communication, and the other characterizing the information about the final state, useful in state-preparation and control. Here we are interested in understanding the properties of these measures, and the information gathering capacities of quantum and classical measurements. We provide a partial answer to the question `in what sense does information gain increase with initial uncertainty?' by showing that, for classical and quantum measurements which are symmetric with respect to reversible transformations of the state space, the information gain regarding the initial state always increases with the observer's initial uncertainty. In addition, we calculate the capacity of all unitarily covariant and commutative permutation-symmetric measurements for obtaining classical information. While it is the von Neumann entropy of the effects which appears in the latter capacity, it is the subentropy which appears in the expression for the former.
Posted Content•
TL;DR: By using local quantum teleportation of a fixed state to one qubit of an entangled pair sent from the other party, it is shown how one party can commit a bit with only classical information as evidence that results in an unconditionally secure protocol.
Abstract: By using local quantum teleportation of a fixed state to one qubit of an entangled pair sent from the other party, it is shown how one party can commit a bit with only classical information as evidence that results in an unconditionally secure protocol. The well-known ``impossibility proof'' does not cover such protocols due to its different commitment and opening prescriptions, which necessitate actual quantum measurements among different possible systems that cannot be entangled as a consequence.
Posted Content•
TL;DR: A protocol of quantum communication is proposed in terms of the multi-qubit quantum telepor-tation through cluster states (Phys. Rev. 86, 910 (2001)).
Abstract: Institute of Theoretical Physics, The Chinese Academy of Sciences, Beijing, 100080, China(Dated: February 9, 2008)A protocol of quantum communication is proposed in terms of the multi-qubit quantum telepor-tation through cluster states (Phys. Rev. Lett. 86, 910 (2001)). Extending the cluster state basedquantum teleportation on the basic unit of three qubits (or qudits), the corresponding multi-qubitnetwork is constructed for both the qubits and qudits (multi-level) cases. The classical informationcosts to complete this communication task is also analyzed. It is also shown that this quantumcommunication protocol can be implemented in the spin-spin system on lattices.
TL;DR: A surprising amount of structure is revealed even for this simple case, which suggests that relationships between quantum and classical information could in general be very intricate.
Abstract: We consider situations in which (i) Alice wishes to send quantum information to Bob via a noisy quantum channel, (ii) Alice has a classical description of the states she wishes to send, and (iii) Alice can make use of a finite amount of noiseless classical information. After setting up the problem in general, we focus attention on one specific scenario in which Alice sends a known qubit down a depolarizing channel along with a noiseless classical bit. We describe a protocol that we conjecture is optimal and calculate the average fidelity obtained. A surprising amount of structure is revealed even for this simple case, which suggests that relationships between quantum and classical information could in general be very intricate.
TL;DR: In this paper, an experimental demonstration of the process of cloning of N = 1 input qubit into M = 2 output qubits by a quantum-injected optical parametric amplifier OPA is presented.
Abstract: An arbitrary quantum state cannot be “cloned” perfectly, i.e. reproduced with “fidelity” F = 1 into M > 1 states identical to the original by any conceivable physical device. The main root of this impossibility resides in the linearity of quantum mechanics. A second “quantum impossibility” process, based on the complete positivity character of any quantum operation and conceivably subtly related to the first one, forbids the realization of a universal NOT gate i.e. one that flips exactly any input qubit into an orthogonal one. A detailed investigation of these results, representing the most fundamental difference between classical and quantum information, indeed can reveal the detailed structure of the latter one. We report an experimental demonstration of the process of cloning of N = 1 input qubit into M = 2 output qubits by a quantum-injected optical parametric amplifier OPA. By the same apparatus the realization of a universal NOT gate is also demonstrated. The two processes will be found to be “universal” and optimal, i.e. the measured fidelity of both processes F < 1 will be found close to the theoretical values.
Journal Article•
TL;DR: In this article, a mixed two-mode squeezed state in Hilbert-Schmidt space with coherent state representation and operators is described. But the authors do not show directly how the teleported state is related to the original state.
Abstract: Quantum teleportation for continuous variables is generally described in phase space by using the Wigner functions. We study quantum teleportation via a mixed two-mode squeezed state in Hilbert-Schmidt space by using the coherent-state representation and operators. This shows directly how the teleported state is related to the original state.