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Probabilistic one-time programs using quantum entanglement
It is well known that quantum technology allows for an unprecedented level of
data and software protection for quantum computers as well as for
quantum-assisted classical computers. To exploit these properties,
probabilistic one-time programs have been developed, where the encoding of
classical software in small quantum states enables computer programs that can
be used only once. Such self-destructing one-time programs facilitate a variety
of new applications reaching from software distribution to one-time delegation
of signature authority. Whereas first proof-of-principle experiments
demonstrated the feasibility of such schemes, the practical applications were
limited due to the requirement of using the software on-the-fly combined with
technological challenges due to the need for active optical switching and a
large amount of classical communication. Here we present an improved protocol
for one-time programs that resolves major drawbacks of previous schemes, by
employing entangled qubit pairs. This results in four orders of magnitude
higher count rates as well the ability to execute a program long after the
quantum information exchange has taken place. We demonstrate our protocol over
an underground fiber link between university buildings in downtown Vienna.
Finally, together with our implementation of a one-time delegation of signature
authority this emphasizes the compatibility of our scheme with
prepare-and-measure quantum internet networks
Judging Voucher Programs One at a Time
The Honorable James J. Gilvary Symposium on Law, Religion & Social Justice: Symposium Essa
Quantum one-time programs
A one-time program is a hypothetical device by which a user may evaluate a circuit on exactly one input of his choice, before the device self-destructs. One-time programs cannot be achieved by software alone, as any software can be copied and re-run. However, it is known that every circuit can be compiled into a one-time program using a very basic hypothetical hardware device called a one-time memory. At first glance it may seem that quantum information, which cannot be copied, might also allow for one-time programs. But it is not hard to see that this intuition is false: one-time 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 one-time programs for quantum circuits? Our main result is that any quantum circuit can be compiled into a one-time program assuming only the same basic one-time memory devices used for classical circuits. Moreover, these quantum one-time programs achieve statistical universal composability (UC-security) 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 UC-security of a recent protocol for delegated quantum computation
On Quasi-Interpretations, Blind Abstractions and Implicit Complexity
Quasi-interpretations are a technique to guarantee complexity bounds on
first-order functional programs: with termination orderings they give in
particular a sufficient condition for a program to be executable in polynomial
time, called here the P-criterion. We study properties of the programs
satisfying the P-criterion, in order to better understand its intensional
expressive power. Given a program on binary lists, its blind abstraction is the
nondeterministic program obtained by replacing lists by their lengths (natural
numbers). A program is blindly polynomial if its blind abstraction terminates
in polynomial time. We show that all programs satisfying a variant of the
P-criterion are in fact blindly polynomial. Then we give two extensions of the
P-criterion: one by relaxing the termination ordering condition, and the other
one (the bounded value property) giving a necessary and sufficient condition
for a program to be polynomial time executable, with memoisation.Comment: 18 page
Tea Time
Tea Time is one of the center's weekly programs that allows students to try tea from around the world
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