Experimental Quantum Teleportation of a Two-Qubit Composite System

Quantum teleportation, a way to transfer the state of a quantum system from one location to another, is central to quantum communication and plays an important role in a number of quantum computation protocols. Previous experimental demonstrations have been implemented with photonic or ionic qubits. Very recently long-distance teleportation and open-destination teleportation have also been realized. Until now, previous experiments have only been able to teleport single qubits. However, since teleportation of single qubits is insufficient for a large-scale realization of quantum communication and computation2-5, teleportation of a composite system containing two or more qubits has been seen as a long-standing goal in quantum information science. Here, we present the experimental realization of quantum teleportation of a two-qubit composite system. In the experiment, we develop and exploit a six-photon interferometer to teleport an arbitrary polarization state of two photons. The observed teleportation fidelities for different initial states are all well beyond the state estimation limit of 0.40 for a two-qubit system. Not only does our six-photon interferometer provide an important step towards teleportation of a complex system, it will also enable future experimental investigations on a number of fundamental quantum communication and computation protocols such as multi-stage realization of quantum-relay, fault-tolerant quantum computation, universal quantum error-correction and one-way quantum computation.Comment: 16pages, 4 figure

Validation Of The Ebmt Risk Score In Chronic Myeloid Leukemia In Brazil And Allogeneic Transplant Outcome.

The management of chronic myeloid leukemia (CML) has changed radically since the introduction of imatinib therapy. The decision of whether to offer a patient a hematopoietic stem cell transplant (HSCT) must be based on the probability of success of the procedure. The aim of this retrospective analysis of 1,084 CML patients who received an allogeneic HSCT in 10 Brazilian Centers between February 1983 and March 2003 was to validate the EBMT risk score. The study population comprised 647 (60%) males and 437 (40%) females, with a median age of 32 years old (range 1 - 59); 898 (83%) were in chronic phase, 146 (13%) were in accelerated phase and 40 (4%) were in blast crisis; 151 (14%) were younger than 20 years old, 620 (57%) were between 20 and 40 and 313 (29%) were older than 40; 1,025 (94%) received an HLA fully matched sibling transplant and only 59 (6%) received an unrelated transplant. In 283 cases (26%) a male recipient received a graft from a female donor. The interval from diagnosis to transplantation was less than 12 months in 223 (21%) cases and greater in 861 (79%). The overall survival, disease-free survival, transplant-related mortality and relapse incidence were 49%, 50%, 45% and 25%, respectively. Of the 1084 patients, 179 (17%) had a risk score of 0 or 1, 397 (37%) had a score of 2, 345 (32%) had a score of 3, 135 (12%) had a score of 4 and 28 (2%) a score of 5 or 6. The overall survival (OS) rate in patients with risk scores 0-1 and 2 was similar (58% and 55%, respectively) but significantly better than that in patients with scores 3 or more (score 3 - 44%, 4 - 36 % and 5-6 - 27%, respectively) pp<0.001). Disease-free survival (DFS) and transplant related mortality (TRM) in a patients with a score of 3 or more were 46% and 49%, respectively and the relapse rate beyond score 5-6 was 77%. Disease status had a negative impact on all outcomes (OS, DFS, TRM, and relapse). The OS rate for male recipients of a graft from a female donor was 40% compared to 52% among the other donor-recipient pairs (p=0.004). DFS and TRM were significant for disease phase and female donor-male recipient (p<0.001 and p<0.003, respectively). In our experience, age and interval between diagnosis and transplant did influence OS, DFS, TRM, and relapse rate. Our results validate the EBMT risk score in the context of a developing country and confirm its usefulness for making point decisions in the imatinib era.90232-

ESR experiments on the Kondo insulator CeNiSn

Below a characteristic temperature, due to hybridisation effects Kondo insulators exhibit a gap in the electronic density of states and behave like semiconductors. By using Gd3+ electron spin resonance (ESR), the compound CeNiSn was investigated as a representative of this class. In addition, the metal-to-insulator transition was studied as a function of doping for CeNi(1-x)Co(x)Sn and CeNi(1-y)Pt(y)Sn. The linewidth of the Gd resonance yields direct information about the density of states at the Fermi energy. So the size of the gap can clearly be estimated for the pure compound, and the closing of the gap by substitution of Ni by Co or Pt can be followed in detail. These results are compared to measurements of NMR, specific heat and susceptibility.Comment: 6 pages including 7 figures, submitted to Phys. Rev.