Quantum repeater

A quantum repeater link, comprising:

• a first transmitter portion that includes:
• a first source of a first probe pulse in a first probe state having components with different photon numbers;
• a first set of matter systems that respectively store qubits, wherein each matter system has a first quantum state and a second quantum state that provide basis states for the qubit stored in the matter system and wherein the first quantum state is capable of interacting with photons in the first probe pulse to change a phase space location of the first probe state;
• and
• a first optical system capable of directing the probe pulse for interaction with one of the matter systems and directing light emerging from the matter system for transmission on a first channel;
• a second transmitter portion that includes:
• a second source of a second probe pulse in a second probe state having components with different photon numbers;
• a second set of matter systems, wherein each matter system has at least one state that is capable of interacting with the photons in the second probe pulse to change the phase space location of the second probe state;
• and
• a second optical system capable of directing the second probe pulse for interaction with one of the matter systems in the second set and directing light emerging from the matter system for transmission on a second channel;
• and
• a measurement station coupled to the first and second channels.

A quantum communication system comprising a plurality of links, wherein in each of the links comprises:

• a first photonic channel;
• a first station connected to a first end of the first photonic channel, the first station including:
• a source of a first probe pulse in a probe state having components with different photon numbers;
• a first set of matter systems, wherein each matter system has at least one quantum state capable of interacting with photons in the first probe pulse to change a phase space location of the probe state;
• and
• a first optical system capable of directing the first probe pulse for interaction with one of the matter systems and directing light emerging from the matter system for transmission on the first photonic channel;
• and
• a second station connected to a second end of the first photonic channel, wherein the second station comprises:
• a second set of matter systems, wherein each matter system in the second set has at least one quantum state capable of interacting with the photons in the first probe pulse to change the phase space location;
• a measurement system;
• and
• a second optical system capable of directing light received from the first photonic channel for interaction with one of the matter systems in the second set and directing light emerging from the matter system into the measurement system.

A quantum communication system comprising a plurality of links, wherein each of the links further comprises:

• a first photonic channel;
• a first station connected to a first end of the first photonic channel, the first station including:
• a source of a first probe pulse in a probe state having components with different photon numbers;
• a first set of matter systems, wherein each matter system has at least one quantum state capable of interacting with photons in the first probe pulse to change a phase space location of the probe state;
• and
• a first optical system capable of directing the first probe pulse for interaction with one of the matter systems and directing light emerging from the matter system for transmission on the first photonic channel;
• and
• a second station connected to a second end of the first photonic channel a second photonic channel having a first end connected to the second station;
• and
• a third station connected to a second end of the second photonic channel, wherein:
• the third station can transmit a second probe pulse through the second photonic channel to the second station;
• and
• the second station comprises a measurement system adapted to measure the first and second probe pulses.

A process for implementing a quantum gate, comprising:

• directing a probe pulse that is in a probe state into a first matter system that is in a first state representing a first qubit, wherein interaction of the probe pulse with the first matter system causes a conditional phase shift in the probe state;
• performing a first displacement operation on the probe pulse, wherein the first displacement operation introduces a first displacement to the probe pulse;
• directing the probe pulse into a second matter system that is in a second state representing a second qubit, wherein interaction of the probe pulse with the second matter system causes a conditional phase shift in the probe state;
• performing a second displacement operation on the probe pulse, wherein the second displacement operation introduces a second displacement to the probe pulse, the second displacement being a complex conjugate of the first displacement;
• directing the probe pulse back into the first matter system, wherein further interaction of the probe pulse with the first matter system causes a conditional phase shift in the probe state;
• performing a third displacement operation on the probe pulse, wherein the third displacement operation introduces a third displacement to the probe pulse, the third displacement being a negative of the first displacement;
• and
• directing the probe pulse back into the second matter system, wherein further interaction of the probe pulse with the second matter system causes a conditional phase shift in the probe state.

A process for implementing a quantum gate, comprising

• performing a first displacement operation on a probe pulse that is in a probe state, wherein the first displacement operation introduces a first displacement to the probe state;
• directing the probe pulse into a first matter system that is in a first state representing a first qubit, wherein interaction of the probe pulse with the first matter system causes a first conditional phase shift in the probe state;
• performing a second displacement operation on the probe pulse, wherein the second displacement operation introduces a second displacement to the probe state;
• performing a second conditional phase shift on the probe state;
• and
• performing a third displacement operation on the probe pulse, wherein the third displacement operation introduces a third displacement to the probe state, the third displacement being equal to the first displacement.