A system and method for distributing a quantum key from a first party to a second party. A first node is connected to a public channel, wherein the first node includes a pulse position modulation encoder connected to a quantum channel. A second node is connected to the public channel, wherein the second node includes a pulse position modulation decoder connected to the quantum channel. The pulse position modulation encoder encodes quantum states |0> and |1>, and transmits the encoded quantum states from the first node to the second node via the quantum channel. Quantum state |1> is encoded as |1>≡(|t1>+|t2>)/√{square root over (2)}.