About Me
I am a graduate student in computer science at MIT, where I am privileged to be advised by Piotr Indyk.
I work primarily on sketching problems in machine learning.
I am broadly interested in the design and analysis of algorithms, especially when it involves randomness and applications to large data sets.
Previously, I graduated from
Caltech with a degree in
computer science in 2016.
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”,
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 tilebased assembly, and showed that the CRNTAM can perform several tasks related to the simulation of Turing machines and construction of algorithmic shapes with lower space or program complexity than in either of its parent models. Here, we introduce a kinetic variant of the CRNTAM and investigate the time complexity of computation and construction. We analyze the time complexity of decision problems in the CRNTAM, and show that decidable languages can be decided as efficiently by CRNTAM programs as by Turing machines. We also 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 CRNTAM programs can decide languages in NTIME ∩ coNTIME(f(n)) in O(f(n) + n + log c) time with (1  exp (c)) probability, using volume exponential in n. 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.
Contact
 Email:
 Office:
 MIT CSAIL, room 32G580