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High-dimensional quantum cryptography with twisted light
Quantum key distribution (QKD) systems often rely on polarization of light for encoding, thus limiting the amount of information that can be sent per photon and placing tight bounds on the error rates that such a system can tolerate. Here we describe a proof-of-principle experiment that indicates the feasibility of high-dimensional QKD based on the transverse structure of the light field allowing for the transfer of more than 1 bit per photon. Our implementation uses the orbital angular momentum (OAM) of photons and the corresponding mutually unbiased basis of angular position (ANG). Our experiment uses a digital micro-mirror device for the rapid generation of OAM and ANG modes at 4 kHz, and a mode sorter capable of sorting single photons based on their OAM and ANG content with a separation efficiency of 93%. Through the use of a seven-dimensional alphabet encoded in the OAM and ANG bases, we achieve a channel capacity of 2.05 bits per sifted photon. Our experiment demonstrates that, in addition to having an increased information capacity, multilevel QKD systems based on spatial-mode encoding can be more resilient against intercept-resend eavesdropping attacks.
Journal Article
Variational quantum compiling with double Q-learning
Quantum compiling aims to construct a quantum circuit V by quantum gates drawn from a native gate alphabet, which is functionally equivalent to the target unitary U . It is a crucial stage for the running of quantum algorithms on noisy intermediate-scale quantum (NISQ) devices. However, the space for structure exploration of quantum circuit is enormous, resulting in the requirement of human expertise, hundreds of experimentations or modifications from existing quantum circuits. In this paper, we propose a variational quantum compiling (VQC) algorithm based on reinforcement learning, in order to automatically design the structure of quantum circuit for VQC with no human intervention. An agent is trained to sequentially select quantum gates from the native gate alphabet and the qubits they act on by double Q -learning with ϵ -greedy exploration strategy and experience replay. At first, the agent randomly explores a number of quantum circuits with different structures, and then iteratively discovers structures with higher performance on the learning task. Simulation results show that the proposed method can make exact compilations with less quantum gates compared to previous VQC algorithms. It can reduce the errors of quantum algorithms due to decoherence process and gate noise in NISQ devices, and enable quantum algorithms especially for complex algorithms to be executed within coherence time.
Journal Article
Alphabetical : how every letter tells a story
\"How on Earth did we fix upon our twenty-six letters, what do they really mean, and how did we come to write them down in the first place? Michael Rosen takes you on an unforgettable adventure through the history of the alphabet in twenty-six vivid chapters, fizzing with personal anecdotes and fascinating facts. Starting with the mysterious Phoenicians and how sounds first came to be written down, he races on to show how nonsense poems work, pins down the strange story of OK, traces our five lost letters and tackles the tyranny of spelling, among many many other things. His heroes of the alphabet range from Edward Lear to Phyllis Pearsall (the inventor of the A-Z), and from the two scribes of Beowulf to rappers. Each chapter takes on a different subject - whether it's codes, umlauts or the writing of dictionaries. Rosen's enthusiasm for letters positively leaps off the page, whether it's the story of his life told through the typewriters he's owned or a chapter on jokes written in a string of gags and word games. This is the book for anyone who's ever wondered why Hawaiian only has a thirteen-letter alphabet or how exactly to write down the sound of a wild raspberry\"-- Provided by publisher.
Book
The Letter and the Cosmos
From our first ABCs to the Book of Revelation’s statement that Jesus is “the Alpha and Omega,” we see the world through our letters. More than just a way of writing, the alphabet is a powerful concept that has shaped Western civilization and our daily lives. In The Letter and the Cosmos , Laurence de Looze probes that influence, showing how the alphabet has served as a lens through which we conceptualize the world and how the world, and sometimes the whole cosmos, has been perceived as a kind of alphabet itself. Beginning with the ancient Greeks, he traces the use of alphabetic letters and their significance from Plato to postmodernism, offering a fascinating tour through Western history.
A sharp and entertaining examination of how languages, letterforms, orthography, and writing tools have reflected our hidden obsession with the alphabet, The Letter and the Cosmos is illustrated with copious examples of the visual and linguistic phenomena which de Looze describes. Read it, and you’ll never look at the alphabet the same way again.
eBook
Human-level concept learning through probabilistic program induction
People learning new concepts can often generalize successfully from just a single example, yet machine learning algorithms typically require tens or hundreds of examples to perform with similar accuracy. People can also use learned concepts in richer ways than conventional algorithms—for action, imagination, and explanation. We present a computational model that captures these human learning abilities for a large class of simple visual concepts: handwritten characters from the world's alphabets. The model represents concepts as simple programs that best explain observed examples under a Bayesian criterion. On a challenging one-shot classification task, the model achieves human-level performance while outperforming recent deep learning approaches. We also present several \"visual Turing tests\" probing the model's creative generalization abilities, which in many cases are indistinguishable from human behavior.
Journal Article
