  The numerical simulation of quantum circuits is an indispensable tool for
development, verification and validation of hybrid quantum-classical algorithms
on near-term quantum co-processors. The emergence of exascale high-performance
computing (HPC) platforms presents new opportunities for pushing the boundaries
of quantum circuit simulation. We present a modernized version of the Tensor
Network Quantum Virtual Machine (TNQVM) which serves as a quantum circuit
simulation backend in the eXtreme-scale ACCelerator (XACC) framework. The new
version is based on the general purpose, scalable tensor network processing
library, ExaTN, and provides multiple configurable quantum circuit simulators
enabling either exact quantum circuit simulation via the full tensor network
contraction, or approximate quantum state representations via suitable tensor
factorizations. Upon necessity, stochastic noise modeling from real quantum
processors is incorporated into the simulations by modeling quantum channels
with Kraus tensors. By combining the portable XACC quantum programming frontend
and the scalable ExaTN numerical backend we introduce an end-to-end virtual
quantum development environment which can scale from laptops to future exascale
platforms. We report initial benchmarks of our framework which include a
demonstration of the distributed execution, incorporation of quantum
decoherence models, and simulation of the random quantum circuits used for the
certification of quantum supremacy on the Google Sycamore superconducting
architecture.
