  The advanced notebooks, mobile phones, and internet applications in today's
world that we use are all entrenched in classical communication bits of zeros
and ones. Classical internet has laid its foundation originating from the
amalgamation of mathematics and Claude Shannon's theory of information. But
today's internet technology is a playground for eavesdroppers. This poses a
serious challenge to various applications that relies on classical internet
technology. This has motivated the researchers to switch to new technologies
that are fundamentally more secure. Exploring the quantum effects, researchers
paved the way into quantum networks that provide security, privacy and range of
capabilities such as quantum computation, communication and metrology. The
realization of quantum internet requires quantum communication between various
remote nodes through quantum channels guarded by quantum cryptographic
protocols. Such networks rely upon quantum bits (qubits) that can
simultaneously take the value of zeros and ones. Due to extraordinary
properties of qubits such as entanglement, teleportation and superposition, it
gives an edge to quantum networks over traditional networks in many ways. But
at the same time transmitting qubits over long distances is a formidable task
and extensive research is going on quantum teleportation over such distances,
which will become a breakthrough in physically realizing quantum internet in
near future. In this paper, quantum internet functionalities, technologies,
applications and open challenges have been extensively surveyed to help readers
gain a basic understanding of infrastructure required for the development of
global quantum internet.
