In a general aspect, a quantum streaming kernel processes a data stream. In some aspects, an input stream of data is converted to an output stream of data by repeatedly receiving new portions of the input stream; encoding each new portion into an internal quantum state of a quantum processor; measuring a first part of the internal quantum state while maintaining coherence of a second part of the internal quantum state; and producing the output stream of data based on the measurements. In some cases, a history of the input stream is preserved by the coherence of the internal quantum state, and the measurements contain information based on the history of the input stream.

In a general aspect, a quantum streaming kernel processes a data stream. In some aspects, an input stream of data is converted to an output stream of data by repeatedly receiving new portions of the input stream; encoding each new portion into an internal quantum state of a quantum processor; measuring a first part of the internal quantum state while maintaining coherence of a second part of the internal quantum state; and producing the output stream of data based on the measurements. In some cases, a history of the input stream is preserved by the coherence of the internal quantum state, and the measurements contain information based on the history of the input stream.

Methods, systems and apparatus for producing quantum circuits with low T gate counts. In one aspect, a method for performing a temporary logical AND operation on two control qubits includes the actions of obtaining an ancilla qubit in an A-state; computing a logical-AND of the two control qubits and storing the computed logical-AND in the state of the ancilla qubit, comprising replacing the A-state of the ancilla qubit with the logical-AND of the two control qubits; maintaining the ancilla qubit storing the logical-AND of the two controls until a first condition is satisfied; and erasing the ancilla qubit when the first condition is satisfied.

Methods, systems and apparatus for producing quantum circuits with low T gate counts. In one aspect, a method for performing a temporary logical AND operation on two control qubits includes the actions of obtaining an ancilla qubit in an A-state; computing a logical-AND of the two control qubits and storing the computed logical-AND in the state of the ancilla qubit, comprising replacing the A-state of the ancilla qubit with the logical-AND of the two control qubits; maintaining the ancilla qubit storing the logical-AND of the two controls until a first condition is satisfied; and erasing the ancilla qubit when the first condition is satisfied.

Generalizations of quantum amplitude amplification and amplitude estimation algorithms work with non-boolean oracles (by way of definition, the action of a non-boolean oracle U.sub.φ on an eigenstate |x is to apply a state-dependent phase-shift φ(x); unlike boolean oracles, the eigenvalues exp(iφ(x)) of a non-boolean oracle are not restricted to be ±1). The non-boolean amplitude amplification algorithm preferentially amplifies the amplitudes of the eigenstates based on the value of φ(x). Starting from a given initial superposition state |ψ.sub.0, the basis states with lower values of cos(φ) are amplified at the expense of the basis states with higher values of cos(φ). The non-boolean quantum mean estimation algorithm uses quantum phase estimation to estimate the expectation ψ.sub.0|U.sub.φ|ψ.sub.0 (i.e., the expected value of exp(iφ(x)) for a random x sampled by making a measurement on |ψ.sub.0). The quantum mean estimation algorithm offers a quadratic speedup over its counterpart boolean algorithm known in the art.

Generalizations of quantum amplitude amplification and amplitude estimation algorithms work with non-boolean oracles (by way of definition, the action of a non-boolean oracle U.sub.φ on an eigenstate |x is to apply a state-dependent phase-shift φ(x); unlike boolean oracles, the eigenvalues exp(iφ(x)) of a non-boolean oracle are not restricted to be ±1). The non-boolean amplitude amplification algorithm preferentially amplifies the amplitudes of the eigenstates based on the value of φ(x). Starting from a given initial superposition state |ψ.sub.0, the basis states with lower values of cos(φ) are amplified at the expense of the basis states with higher values of cos(φ). The non-boolean quantum mean estimation algorithm uses quantum phase estimation to estimate the expectation ψ.sub.0|U.sub.φ|ψ.sub.0 (i.e., the expected value of exp(iφ(x)) for a random x sampled by making a measurement on |ψ.sub.0). The quantum mean estimation algorithm offers a quadratic speedup over its counterpart boolean algorithm known in the art.

One example describes a superconducting XOR-gate system. The system includes a pulse generator configured to generate a decision pulse. The system also includes an input superconducting XOR-2 gate that receives a first superconducting logic input signal and a second superconducting logic input signal and is configured to perform a logic XOR function based on the decision pulse on a given phase of a clock signal to provide an intermediate superconducting logic output signal. The system also includes an output superconducting XOR-2 gate that receives the intermediate superconducting logic output signal and a third superconducting logic input signal and is configured to perform a logic XOR function based on the decision pulse on the given phase of the clock signal to provide a superconducting logic output signal.

One example describes a superconducting XOR-gate system. The system includes a pulse generator configured to generate a decision pulse. The system also includes an input superconducting XOR-2 gate that receives a first superconducting logic input signal and a second superconducting logic input signal and is configured to perform a logic XOR function based on the decision pulse on a given phase of a clock signal to provide an intermediate superconducting logic output signal. The system also includes an output superconducting XOR-2 gate that receives the intermediate superconducting logic output signal and a third superconducting logic input signal and is configured to perform a logic XOR function based on the decision pulse on the given phase of the clock signal to provide a superconducting logic output signal.

One example includes an isochronous receiver system. The system includes a pulse receiver configured to receive an input data signal from a transmission line and to convert the input data signal to a pulse signal. The system also includes a converter system comprising a phase converter system. The phase converter system includes a plurality of pulse converters associated with a respective plurality of sampling windows across a period of an AC clock signal. At least two of the sampling windows overlap at any given phase of the AC clock signal, such that the converter system is configured to generate an output pulse signal that is phase-aligned with at least one of a plurality of sampling phases of the AC clock signal based on associating the pulse signal with at least two of the sampling windows.

One example includes an isochronous receiver system. The system includes a pulse receiver configured to receive an input data signal from a transmission line and to convert the input data signal to a pulse signal. The system also includes a converter system comprising a phase converter system. The phase converter system includes a plurality of pulse converters associated with a respective plurality of sampling windows across a period of an AC clock signal. At least two of the sampling windows overlap at any given phase of the AC clock signal, such that the converter system is configured to generate an output pulse signal that is phase-aligned with at least one of a plurality of sampling phases of the AC clock signal based on associating the pulse signal with at least two of the sampling windows.