Open Source Quantum Computing

Unlike a electronic semiconductor machine which uses a bit for memory representation, in a quantum computer the quantum-bit (qbit) represents a state, essentially making direct use of quantum mechanical such as superposition of states etc to perform operations.

Wikipedia has a quick overview of Quantum Computing
https://en.wikipedia.org/wiki/Quantum_computing

There has been recent news about companies making their quantum computing infrastructure software available, notably D-Wave.

Jonathon Narvey of BetaKit covers it here
http://betakit.com/d-wave-open-sources-software-tool-to-build-foundation-for-a-quantum-computing-community/

Klint Finley of Wired covers it here
https://www.wired.com/2017/01/d-wave-turns-open-source-democratize-quantum-computing/

Open Source Tools

Some interesting foundational software tools have become available as open source.

D-Wave, releases a decomposing solver
https://github.com/dwavesystems/qbsolv

Quantum Macro Assembler for D-Wave systems by LANL
https://github.com/lanl/qmasm

Since it is quite difficult to have access to a 'real' quantum machine, there is a good need for 'simulator's.

jQuantum by Andreas de Vries is a program which simulates a quantum computer.
http://jquantum.sourceforge.net/

In addition to the simulators, there are also multiple libraries in C/C++ that have become available now. A good list is available at Quantiki.
https://www.quantiki.org/wiki/list-qc-simulators

However, there is more work to do, in terms of having access to the actual machines, even if for very short time periods to explore and get a feel.

Meanwhile, if you want to try and learn basics of Quantum Computing, the book by Michael Nielsen and Isaac Chuang, titled "Quantum Computation and Quantum Information" is a good place to start.