• Hao-Chung Cheng (QCIS, UTS)
    • Title: On the Concavity of Auxiliary Function in Classical-Quantum Channels
    • Abstract: The auxiliary function of a classical channel appears in two fundamental quantities that upper and lower bound the error probability, respectively. A crucial property of the auxiliary function is its concavity, which leads to several important results in finite block length analysis. In this paper, we prove that the auxiliary function of a classical-quantum channel also enjoys the same concave property, extending an earlier partial result to its full generality. The key component in our proof is a beautiful result of geometric means of operators. (Joint work with Min-Hsiu Hsieh. arXiv:1602.03297)
  • Prof Runyao Duan (QCIS, UTS)
    • Title: On the zero-error capacities of noisy quantum channels
    • Abstract: In 1956 Shannon introduced the notion of zero-error capacity to characterise the ability of a noisy (classical) channel to transmit classical information with zero probability of error. Since Shannon’s seminal work, the study of this notion and the related topics has grown into a vast field called zero-error information theory. Recently there are considerable interest in developing a quantum zero-error information theory by considering quantum effects in zero-error communication. In this talk we first review several major progresses on this topic. Then we focus on an unexpected connected connection between zero-error communication and operator algebras via a mathematical tool called noncommutative graphs, which enables us to introduce a quantum generalisation of the celebrated Lovász number. We then show that auxiliary resources such as entanglement, feedback, and no-signalling correlations can not only significantly increase the capacity, but also make relevant problems much more feasible. As a notable example, we show that the classic Lovász number is exactly the zero-error classical capacity of a graph assisted by quantum no-signalling correlations, which is the first complete information-theoretic interpretation of the Lovász number since 1979.  (This talk is mainly based on the following three papers: [1] Runyao Duan, Simone Severini and Andreas Winter, “Zero-error communication via quantum channels, noncommutative graphs and a quantum Lovász number,” IEEE Transactions on Information Theory, vol. 59, no. 2, pp. 1164–1174 (2013), arXiv: 1002.2514. [2] Runyao Duan and Andreas Winter, “No-signalling-assisted zero-error capacity of quantum channels and an information theoretic interpretation of the Lovász number”, IEEE Transactions on Information Theory, vol. 62, no. 2, pp. 891-914 (2016), arXiv: 1409.3426.  [3] Runyao Duan, Simone Severini and Andreas Winter, “On zero-error communication via quantum channels in the presence of noiseless feedback”, Accepted in IEEE Transactions on Information Theory in April 2016, arXiv: 1502.02987.)
  • A/Prof Steven T. Flammia (Quantum Physics Group, USyd)
    • Title: Sparse Quantum Codes from Quantum Circuits
    • Abstract: We describe a general method for turning quantum circuits into sparse quantum subsystem codes. Using this prescription, we can map an arbitrary stabilizer code into a new subsystem code with the same distance and number of encoded qubits but where all the generators have constant weight, at the cost of adding some ancilla qubits. With an additional overhead of ancilla qubits, the new code can also be made spatially local. Applying our construction to certain concatenated stabilizer codes yields families of subsystem codes with constant-weight generators and with minimum distance d=n1−ε, where ε=O(1/logn‾‾‾‾‾√). For spatially local codes in D dimensions we nearly saturate a bound due to Bravyi and Terhal and achieve d=n1−ε−1/D. Previously the best code distance achievable with constant-weight generators in any dimension, was due to Freedman, Meyer and Luo.
  • Rana Abbas (EIE, USyd)
    • Title: Random Multiple Access for M2M Communications with QoS Guarantees
    • We propose a novel random multiple access scheme with quality of service (QoS) guarantees for machine-to-machine (M2M) communications. We consider a slotted uncoordinated data transmission period during which machine type communication (MTC) devices transmit over the same radio channel. MTC devices are grouped based on their QoS requirements, and each group is assigned an access probability. Based on the assigned probabilities, in each time slot, an MTC device decides to transmit a replica of its packet or remain silent. Therefore, in each time slot, the base station (BS) receives a superposition of packets from different MTCs of different groups. The BS employs successive interference cancellation (SIC) to recover all the devices’ packets. By drawing an analogy between our random multiple access scheme and the unequal-recovery-time property of codes-on-graph, we formulate the SIC process in the proposed RMA scheme based on the AND-OR tree, and we derive the closed form expressions for the average probability of device resolution for each group. We use the analytical expressions to design the access probabilities, and we validate the accuracy of the expressions through Monte Carlo simulations. We show that the designed access probabilities can guarantee the QoS requirements with high probabilities and high energy efficiency. Finally, we compare our proposed random multiple access scheme with existing M2M coordinated access schemes and present the cases where our proposed scheme outperforms the latter.
  • Dr Lawrence Ong (University of Newcastle) 
    • Title: Index coding - improving broadcast rates using side information
    • Abstract: In many communication systems, the last mile is often the bottleneck. A potential solution to this problem is to utilise local cache, which is also known as side information. Index coding is an information-theoretic study of this setup of broadcasting with side information. This talk will present various techniques used in index coding.
  • Prof Igor Shparlinski (UNSW)
    • Title: Quantum Polynomial Interpolation over Finite Fields
    • Abstract: It will be a survey of some recent (and not so) results related to various modification of the classical polynomial interpolation problem.
  • Dr Marco Tomamichel (Quantum Physics Group, USyd)
    • Title: Characterizing a channel beyond Shannon's capacity: an overview on recent progress
    • Abstract: I will discuss recent progress on the question at the core of Shannon's original theory: how much information can we transmit through a noisy communication channel? Motivated by practical considerations, researchers have since been interested in characterizing channels beyond their capacity, namely to look at the optimal tradeoff between transmission rate, the probability of decoding failure, and the blocklength of the code. I will mostly focus on the classical case, and summarize the current state-of-the-art in applying this theory to quantum channels.
  • Prof Jinhong Yuan (UNSW)
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