7,151 research outputs found
Minimal Representations of Natural Numbers Under a Set of Operators
This paper studies the minimal length representation of the natural numbers.
Let O be a fixed set of integer-valued functions (primarily hyperoperations).
For each n, what is the shortest way of expressing n as a combinations of
functions in O to the constant 1? For example, if O contains the two functions
Sx (successor of x) and *xy (x times y) then the shortest representation of 12
is *SSS1SS1, with 8 symbols. This is taken to mean that 8 is complexity of 12
under O. We make a study of such minimal representations and complexities in
this paper, proving and/or rightly predicting bounds on complexities,
discussing some relevant patterns in the complexities and minimal
representations of the natural numbers and listing the results gleaned from
computational analysis. Computationally, the first 4.5 million natural numbers
were probed to verify our mathematically obtained results. Due to the
finiteness of the problem, we used the method of exhaustion of possibilities to
state some other results as well.Comment: 13 pages, 2 figures, 2 table
Experimental construction of generic three-qubit states and their reconstruction from two-party reduced states on an NMR quantum information processor
We experimentally explore the state space of three qubits on an NMR quantum
information processor. We construct a scheme to experimentally realize a
canonical form for general three-qubit states up to single-qubit unitaries.
This form involves a non-trivial combination of GHZ and W-type maximally
entangled states of three qubits. The general circuit that we have constructed
for the generic state reduces to those for GHZ and W states as special cases.
The experimental construction of a generic state is carried out for a
nontrivial set of parameters and the good fidelity of preparation is confirmed
by complete state tomography. The GHZ and W-states are constructed as special
cases of the general experimental scheme. Further, we experimentally
demonstrate a curious fact about three-qubit states, where for almost all pure
states, the two-qubit reduced states can be used to reconstruct the full
three-qubit state. For the case of a generic state and for the W-state, we
demonstrate this method of reconstruction by comparing it with the directly
tomographed three-qubit state.Comment: Revised version to appear in PRA new results adde
Determining the parity of a permutation using an experimental NMR qutrit
We present the NMR implementation of a recently proposed quantum algorithm to
find the parity of a permutation. In the usual qubit model of quantum
computation, speedup requires the presence of entanglement and thus cannot be
achieved by a single qubit. On the other hand, a qutrit is qualitatively more
quantum than a qubit because of the existence of quantum contextuality and a
single qutrit can be used for computing. We use the deuterium nucleus oriented
in a liquid crystal as the experimental qutrit. This is the first experimental
exploitation of a single qutrit to carry out a computational task.Comment: 6 pages 4 figures revte
Experimental demonstration of quantum contextuality on an NMR qutrit
We experimentally test quantum contextuality of a single qutrit using NMR.
The contextuality inequalities based on nine observables developed by Kurzynski
et. al. are first reformulated in terms of traceless observables which can be
measured in an NMR experiment. These inequalities reveal the contextuality of
almost all single-qutrit states. We demonstrate the violation of the inequality
on four different initial states of a spin-1 deuterium nucleus oriented in a
liquid crystal matrix, and follow the violation as the states evolve in time.
We also describe and experimentally perform a single-shot test of contextuality
for a subclass of qutrit states whose density matrix is diagonal in the energy
basis.Comment: 7 pages revtex 4 figure
Majorana representation, qutrit Hilbert space and NMR implementation of qutrit gates
We report a study of the Majorana geometrical representation of a qutrit,
where a pair of points on a unit sphere represents its quantum states. A
canonical form for qutrit states is presented, where every state can be
obtained from a one-parameter family of states via action. The notion
of spin-1 magnetization which is invariant under is geometrically
interpreted on the Majorana sphere. Furthermore, we describe the action of
several quantum gates in the Majorana picture and experimentally implement
these gates on a spin-1 system (an NMR qutrit) oriented in a liquid crystalline
environment. We study the dynamics of the pair of points representing a qutrit
state under various useful quantum operations and connect them to different NMR
operations. Finally, using the Gell Mann matrix picture we experimentally
implement a scheme for complete qutrit state tomography.Comment: replaced with final version 3 figures adde
Quadratic Chabauty and rational points II: Generalised height functions on Selmer varieties
We give new instances where Chabauty--Kim sets can be proved to be finite, by
developing a notion of "generalised height functions" on Selmer varieties. We
also explain how to compute these generalised heights in terms of iterated
integrals and give the first explicit nonabelian Chabauty result for a curve
whose Jacobian has Mordell-Weil rank larger than its genus
A comparative study of system size dependence of the effect of non-unitary channels on different classes of quantum states
We investigate the effect of different types of non-unitary quantum channels
on multi-qubit quantum systems. For an -qubit system and a particular
channel, in order to draw unbiased conclusions about the system as a whole as
opposed to specific states, we evolve a large number of randomly generated
states under the given channel. We increase the number of qubits and study the
effect of system size on the decoherence processes. The entire scheme is
repeated for various types of environments which include dephasing channel,
depolarising channel, collective dephasing channel and zero temperature bath.
Non-unitary channels representing the environments are modeled via their Karus
operator decomposition or master equation approach. Further, for a given we
restrict ourselves to the study of particular subclasses of entangled states,
namely the GHZ-type and W-type states. We generate random states within these
classes and study the class behaviors under different quantum channels for
various values of .Comment: 10 pages revtex 10 pdf figure
Implementation of the quantum Fourier transform on a hybrid qubit-qutrit NMR quantum emulator
The quantum Fourier transform (QFT) is a key ingredient of several quantum
algorithms and a qudit-specific implementation of the QFT is hence an important
step toward the realization of qudit-based quantum computers. This work
develops a circuit decomposition of the QFT for hybrid qudits based on
generalized Hadamard and generalized controlled-phase gates, which can be
implemented using selective rotations in NMR. We experimentally implement the
hybrid qudit QFT on an NMR quantum emulator, which uses four qubits to emulate
a single qutrit coupled to two qubits.Comment: 7 pages, 5 figure
Energy and System Size Dependence of Photon Production at Forward Rapidities at RHIC
The energy and system size dependence of pseudorapidity () and
multiplicity distributions of photons are measured in the region -2.3
-3.7 for Cu + Cu collisions at = 200 and 62.4
GeV. Photon multiplicity measurements at forward rapidity have been carried out
using a Photon Multiplicity Detector (PMD) in the STAR experiment. Photons are
found to follow longitudinal scaling for Cu + Cu collisions for 0-10%
centrality. A Comparison of pseudorapidity distributions with HIIJING model is
also presented.Comment: 6 PAGES, 6 FIGURES, Poster presented in QM 200
Quantum chaos, thermalization and tunneling in an exactly solvable few body system
Exactly solvable models that exhibit quantum signatures of classical chaos
are both rare as well as important - more so in view of the fact that the
mechanisms for ergodic behavior and thermalization in isolated quantum systems
and its connections to non-integrability are under active investigation. In
this work, we study quantum systems of few qubits collectively modeled as a
kicked top, a textbook example of quantum chaos. In particular, we show that
the 3 and 4 qubit cases are exactly solvable and yet, interestingly, can
display signatures of ergodicity and thermalization. Deriving analytical
expressions for entanglement entropy and concurrence, we see agreement in
certain parameter regimes between long-time average values and ensemble
averages of random states with permutation symmetry. Comparing with results
using the data of a recent transmons based experiment realizing the 3-qubit
case, we find agreement for short times, including a peculiar step-like
behaviour in correlations of some states. In the case of 4-qubits we point to a
precursor of dynamical tunneling between what in the classical limit would be
two stable islands. Numerical results for larger number of qubits show the
emergence of the classical limit including signatures of a bifurcation.Comment: 6+5 pages, 7 figure
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