Add initial org-level README file (#1)

This is an initial README file for the Quantumlib org on GitHub. Once merged, it will be visible to people who go to https://github.com/quantumlib/.

Author: mhucka

profile/README.md

@@ -0,0 +1,40 @@
+The [Quantum AI](https://quantumai.google) team and collaborators from all
+around the world maintain and develop open-source software projects for quantum
+computing. We build best-in-class libraries and utilities to advance research
+into applications and error correction for the future of fault-tolerant quantum
+computing. Our open-source projects are found in repositories under the
+Quantumlib organization and elsewhere on GitHub.
+
+## Repositories
+
+Our major efforts include the following:
+
+*   [Cirq](https://github.com/quantumlib/Cirq): framework for creating,
+    manipulating, and running quantum circuits on hardware or in simulation.
+*   [OpenFermion](https://github.com/quantumlib/OpenFermion): framework for
+    creating and analyzing quantum algorithms to simulate electronic structures.
+*   [qsim](https://github.com/quantumlib/qsim): fast state-vector
+    simulator that integrates with Cirq and TensorFlow Quantum.
+*   [Qualtran](https://github.com/quantumlib/Qualtran): library for expressing
+    and analyzing fault-tolerant quantum algorithms.
+*   [Stim](https://github.com/quantumlib/Stim): tool for high-performance
+    simulation and analysis of quantum stabilizer circuits.
+*   [TensorFlow Quantum](https://github.com/tensorflow/quantum): framework for
+    hybrid quantum-classical machine learning using
+    [TensorFlow](https://tensorflow.org).
+
+Other projects include:
+
+*   [Chromobius](https://github.com/quantumlib/Chromobius): fast Möbius decoder
+    for color codes used in quantum error correction.
+*   [ReCirq](https://github.com/quantumlib/ReCirq): repository of research
+    examples and published experiments that use Cirq.
+*   [Tensor Network Contraction Optimizer (TNCO)](
+    https://github.com/google-research/tnco): high-performance library for
+    tensor networks.
+*   [Tesseract Decoder](https://github.com/quantumlib/tesseract-decoder):
+    search-based decoder for quantum error correction.
+*   [TypedUnits](https://github.com/quantumlib/TypedUnits): utility
+    library for working with units of measurement.
+*   [Unitary](https://github.com/quantumlib/unitary): library for exploring
+    quantum computing concepts through games.