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An adaptive attack on Wiesner’s quantum money,” arXiv:1404.1507 [quantph
"... Unlike classical money, which is hard to forge for practical reasons (e.g. producing paper with a certain property), quantum money is attractive because its security might be based on the nocloning theorem. The first quantum money scheme was introduced by Wiesner circa 1970. Although more sophistic ..."
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Unlike classical money, which is hard to forge for practical reasons (e.g. producing paper with a certain property), quantum money is attractive because its security might be based on the nocloning theorem. The first quantum money scheme was introduced by Wiesner circa 1970. Although more sophisticated quantum money schemes were proposed, Wiesner’s scheme remained appealing because it is both conceptually clean and relatively easy to implement. We show an efficient adaptive attack on Wiesner’s quantum money scheme [Wie83] (and its variant by Bennett et al. [BBBW83]), when valid money is accepted and passed on, while invalid money is destroyed. Our approach is based on interactionfree measurement and the quantum Zeno effect, also known as ElitzurVaidman’s bomb tester. It allows us to break Wiesner’s scheme with 4 possible states per qubit, as well as against generalizations which use more than 4 states per qubit. 1
Quantum onetime programs (short abstract for QCRYPT 2013) ∗
, 2013
"... A onetime program is a hypothetical device by which a user may evaluate a circuit on exactly one input of his choice, before the device selfdestructs. Onetime programs cannot be achieved by software alone, as any software can be copied and rerun. However, it is known that every circuit can be co ..."
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A onetime program is a hypothetical device by which a user may evaluate a circuit on exactly one input of his choice, before the device selfdestructs. Onetime programs cannot be achieved by software alone, as any software can be copied and rerun. However, it is known that every circuit can be compiled into a onetime program using a very basic hypothetical hardware device called a onetime memory. At first glance it may seem that quantum information, which cannot be copied, might also allow for onetime programs. But it is not hard to see that this intuition is false: onetime programs for classical or quantum circuits based solely on quantum information do not exist, even with computational assumptions. This observation raises the question, “what assumptions are required to achieve onetime programs for quantum circuits? ” Our main result is that any quantum circuit can be compiled into a onetime program assuming only the same basic onetime memory devices used for classical circuits. Moreover, these quantum onetime programs achieve statistical universal composability (UCsecurity) against any malicious user. Our construction employs methods for computation on authenticated quantum data, and we present a new quantum authentication scheme called the trap
Quantum onetime programs (extended abstract)
"... Abstract. A onetime program is a hypothetical device by which a user may evaluate a circuit on exactly one input of his choice, before the device selfdestructs. Onetime programs cannot be achieved by software alone, as any software can be copied and rerun. However, it is known that every circuit ..."
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Abstract. A onetime program is a hypothetical device by which a user may evaluate a circuit on exactly one input of his choice, before the device selfdestructs. Onetime programs cannot be achieved by software alone, as any software can be copied and rerun. However, it is known that every circuit can be compiled into a onetime program using a very basic hypothetical hardware device called a onetime memory. At first glance it may seem that quantum information, which cannot be copied, might also allow for onetime programs. But it is not hard to see that this intuition is false: onetime programs for classical or quantum circuits based solely on quantum information do not exist, even with computational assumptions. This observation raises the question, “what assumptions are required to achieve onetime programs for quantum circuits? ” Our main result is that any quantum circuit can be compiled into a onetime program assuming only the same basic onetime memory devices used for classical circuits. Moreover, these quantum onetime programs achieve statistical universal composability (UCsecurity) against any malicious user. Our construction employs methods for computation on authenticated quantum data, and we present a new quantum authentication scheme called the trap scheme for this purpose. As a corollary, we establish UCsecurity of a recent protocol for delegated quantum computation. 1
The Ghost in the Quantum Turing Machine
"... In honor of Alan Turing’s hundredth birthday, I unwisely set out some thoughts about one of Turing’s obsessions throughout his life, the question of physics and free will. I focus relatively narrowly on a notion that I call “Knightian freedom”: a certain kind of inprinciple physical unpredictabilit ..."
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In honor of Alan Turing’s hundredth birthday, I unwisely set out some thoughts about one of Turing’s obsessions throughout his life, the question of physics and free will. I focus relatively narrowly on a notion that I call “Knightian freedom”: a certain kind of inprinciple physical unpredictability that goesbeyond probabilisticunpredictability. Other, moremetaphysicalaspects of free will I regard as possibly outside the scope of science. I examine a viewpoint, suggested independently by Carl Hoefer, Cristi Stoica, and even Turing himself, that tries to find scope for “freedom ” in the universe’s boundary conditions rather than in the dynamical laws. Taking this viewpoint seriously leads to many interesting conceptual problems. I investigate how far one can go toward solving those problems, and along the way, encounter (among other things) the NoCloning Theorem, the measurement problem, decoherence, chaos, the arrow of time, the holographic principle, Newcomb’s paradox, Boltzmann brains, algorithmic information theory, and the Common Prior Assumption. I also compare the viewpoint explored here to the more radical speculations of Roger Penrose. The result of all this is an unusual perspective on time, quantum mechanics, and causation,