About Me
I recently graduated from Caltech where I was a student in the computer science option.
In the fall, I will begin a PhD with the Theory of Computing group at MIT.
I am broadly interested in the design and analysis of algorithms, especially in useful or unusual settings.
In the past, I have done research in several different fields, including information retrieval, computational biophysics, quantum computing, molecular programming, and causal inference.
At Caltech, I was
heavily
involved
in
student
government.
My CV is available.
Publications

Nicholas Schiefer and
Erik Winfree, “Time Complexity of Computation and Construction in the Chemical Reaction NetworkControlled Tile Assembly Model”,
to appear in the 22nd International Conference on DNA Computing and Molecular Programming
(DNA22),
2016.
Abstract
In isolation, chemical reaction networks and tilebased selfassembly are wellstudied models of chemical computation. Previously, we introduced the chemical reaction networkcontrolled tile assembly model (CRNTAM), in which a stochastic chemical reaction network can act as a nonlocal control and signalling system for a tilebased assembly system, and showed that the CRNTAM can perform several tasks related to the simulation of Turing machines and construction of algorithmic shapes with lower program complexity than in either of its parent models. Here, we give a kinetic model for the CRNTAM and investigate the time complexity of Turinguniversal computation and construction of shapes. We analyze the time complexity of decision problems in the CRNTAM, and show that decidable languages can be decided as efficiently by CRN AM programs as on Turing machines and give a lower bound for the spacetime complexity of CRNTAM computation that rules out efficient parallel stack machines. We provide efficient parallel implementations of nondeterministic computations, showing among other things that the CRNTAM can decide problems in NTIME(f(n)) ∩ coNTIME(f(n)) in O(f(n)) time with 1−ε probability if given exponential volume. Lastly, we provide basic mechanisms for parallel computations that share information and illustrate the limits of parallel computation in the CRNTAM.

Nicholas Schiefer and
Erik Winfree, “Universal Computation and Optimal Construction in the Chemical Reaction NetworkControlled Tile Assembly Model”,
21st International Conference on DNA Computing and Molecular Programming
(DNA21),
2015,
Lecture Notes in Computer Science vol. 9211, pp. 34–54.
Abstract
Tilebased selfassembly and chemical reaction networks provide two wellstudied models of scalable DNAbased computation. Although tile selfassembly provides a powerful framework for describing Turinguniversal selfassembling systems, assembly logic in tile selfassembly is localized, so that only the nearby environment can affect the process of selfassembly. We introduce a new model of tilebased selfassembly in which a wellmixed chemical reaction network interacts with selfassembling tiles to exert nonlocal control on the selfassembly process. Through simulation of multistack machines, we demonstrate that this new model is efficiently Turinguniversal, even when restricted to unbounded space in only one spatial dimension. Using a natural notion of program complexity, we also show that this new model can produce many complex shapes with programs of lower complexity. Most notably, we show that arbitrary connected shapes can be produced by a program with complexity bounded by the Kolmogorov complexity of the shape, without the large scale factor that is required for the analogous result in the abstract tile assembly model. These results suggest that controlled selfassembly provides additional algorithmic power over tileonly selfassembly, and that nonlocal control enhances our ability to perform computation and algorithmically selfassemble structures from small input programs.
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